, use meaningful headings (<H1>, <H2>, and so on), and provide meaningful ALT text for images. * Many search engines ignore frames, so avoid them, and be sure to provide useful NOFRAMES content if you do use them. * Most earch engines ignore image maps, forms, and JavaScript, so make sure that navigating your site doesn't depend on them. Provide normal links for site navigation. * Avoid using META refresh, because many search engines penalize sites that use it (META refresh has been used to trick search engines). * The indexing programs of some search engines (including AltaVista and Infoseek) will also take into account <META NAME="keywords" CONTENT="..."> tags that appear in the <HEAD> part of your documents. However, META keywords have been used to trick search engines, so many will ignore your keywords list if you repeat a given keyword too often. At this writing, "to o often" means "more than 7 times" to some popular engines, but that may change in the future as indexing programs are changed to defend against trickery. * If you include a <META NAME="description" CONTENT="..."> tag in the <HEAD> part of your documents, then some search engines will use the content of this tag as your site's description when displaying search results. This won't affect your ranking in searches, but it can help search engine users understand what your site offers when a search does find your site. Note that the CONTENT attribute of the META keywords and description tags may contain up to 1022 characters, but no markup other than entities. You might want to preview your site with a text-only browser like Lynx, to get an idea of how your site appears to search engines. Search Engine Watch at <URL:http://searchenginewatch.com/> is a Web site dedicated to search engines and strategies for Web page authors. 2.4. How do I prevent my site from being indexed by search engines? See <URL:http://info.webcrawler.com/mak/projects/robots/exclusion.html>. 2.5. How do I redirect someone to my new page? The most reliable way is to configure the server to send out a redirection instruction when the old URL is requested. Then the browser will automatically get the new URL. This is the fastest and most efficient way, and is the only wa y described here that can convince indexing robots to phase out the old URL. For configuration details consult your server admin or documentation (with NCSA or Apache servers, use a Redirect statement in .htaccess). If you can't set up a redirect, there are other possibilities. These are inferior because they tell the search engines that there's still a page at the old location, not that the page has moved to a new location. But if it's impossible for you to configure redirection at your server, here are two alternatives: * Put up a small page with text like "This page has moved to http://new.url/ -- please adjust your bookmarks." * A Netscape and MSIE solution, which doesn't work on many other browsers (an d screws up the "back" button in Netscape) is: <META HTTP-EQUIV="Refresh" CONTENT="x; URL=new.URL"> which will load the new URL after x seconds. This should go in the HEAD of the document. But if you do this, also include a short text saying "Documen t moved to new URL so-and-so" for other browsers. (The screwing-up bit refers to the fact that if you press "Back" after you have been redirected, you will be taken to the document with the META refresh. Then the refresh will be activated, and so you'll jump to the page you just tried to leave.) 2.6. How do I password protect my web site? Password protection is done through HTTP authentication. The configuration details vary from server to server, so you should read the authentication section of your server documentation. Contact your server administrator if you need help with this. For example, if your server is Apache, see <URL:http://www.apache.org/docs/misc/FAQ.html#user-authentication>. 2.7. How do I stop my page from being cached? Browsers cache web documents; they store local copies of documents to speed up repeated references to documents that haven't changed. Also, many browsers are configured to use public proxy caches, which serve many users (e.g., all customers of an ISP, or all employees behind a corporate firewall). To effectively control how your documents are cached you must configure your serve r to send appropriate HTTP headers. The configuration details vary from server to server, so check your server documentation. The Expires header is understood by virtually all caches. The cached document will be retrieved again automatically once it has expired. The Expires header must contain an HTTP date, which must be Greenwich Mean Time (GMT), not local time. HTTP 1.1 introduced the Cache-Control header, which provides more flexibility for telling caches how to handle the document. For more information, see the HTTP 1.1 draft (see <http://www.w3.org/Protocols/>). The Pragma header is generally ineffective because its meaning is not standardized and few caches honor it. Using <META HTTP-EQUIV=...> elements in HTML documents is also generally ineffective; some browsers may honor such markup, but other caches ignore it completely. Further discussion can be found at <http://www.mnot.net/cache_docs/>. 2.8. How do I hide my source? You can't. The HTML source is necessary for the browser to display your document; you must send the complete, unencrypted source to the browser. Even i f a particular browser doesn't have a "View Source" feature, there are many that do, and someone can always retrieve the document by hand (using telnet) or from the browser's cache. There are tricks that make it more difficult for some readers to view or save your source (e.g., tricking newbies into thinking there's nothing there by adding dozens of blank lines to the beginning of the document). However, just a s with tricks that try to protect images from being saved, these tricks have very limited effectiveness and can cause various problems for law-abiding users. 2.9. How do I detect what browser is being used? Many browsers identify themselves when they request a document. A CGI script will have this information available in the HTTP_USER_AGENT environment variable, and it can use that to send out a version of the document which is optimized for that browser. Keep in mind not all browsers identify themselves correctly. Microsoft Internet Explorer, for example, claims to be "Mozilla" to get at Netscape enhanced documents. And of course, if a cache proxy keeps the Netscape enhanced document, someone with another browser will also get this document if he goes through the cache. For these reasons and others, it is not a good idea to play the browser guessin g game. 2.10. How do I get my visitors' email addresses? You can't. Although each request for a document is usually logged with the name or address of the remote host, the actual username is almost never logged as well. This is mostly because of performance reasons, as it would require that the server uses the ident protocol to see who is on the other end. This takes time. And if a cache proxy is doing the request, you don't get anything sensible. But just stop to think for a minute... would you really want every single site you visit to know your email address? Imagine the loads of automated thank you' s you would be receiving. If you visited 20 sites, you would get at least 20 emails that day, plus no doubt they would send you invitations to return later. It would be a nightmare as well as an invasion of privacy! In Netscape 2.0, it was possible to automatically submit a form with a mailto a s action, using JavaScript. This would send email to the document's owner, with the address the visitor configured in the From line. Of course, that can be "mickey.mouse@disney.com". This was fixed by Netscape 2.01. The most reliable way is to put up a form, asking the visitor to fill in his email address. To increase the chances that visitors will actually do it, offer them something useful in return. 2.11. Why is my custom 404 message not displayed? Recent versions of Internet Explorer default to "friendly" HTTP error messages. When a special HTTP response (e.g., a 404 response) is shorter than 512 bytes, the browser substitutes its own message for the one delivered by the server. As a user of Internet Explorer, you can disable this feature in the "Advanced" options panel. As a web author, your only recourse is to make the error page larger. 3. Web Design 3.1. How do I include one file in another? HTML itself offers no way to seamlessly incorporate the content of one file int o another. True dynamic inclusion of one HTML document (even in a different "charset") int o another is offered by the OBJECT element, but due to shortcomings of browser versions in current use, it seems unwise to rely on this yet for essential content. The same can be said for IFRAME. Two popular ways of including the contents of one file seamlessly into another for the WWW are preprocessing and server-side inclusion. Preprocessing techniques include the C preprocessor and other generic text manipulation methods, and several HTML-specific processors. But beware of makin g your "source code" non-portable. The HTML can only be validated after pre-processing, so the typical cycle "Edit , Check, Upload" becomes "Edit, Preprocess, Check, Upload" (here, "Check" include s whatever steps you use to preview your pages: validation, linting, management walk-through etc.; and "upload" means whatever you do to finally publish your new pages to the web server). A much more powerful and versatile pre-processing technique is to use an SGML processor (such as the SP package) to generate your HTML; this can be self-validating. Examples of server-side inclusion are Server Side Includes "SSI" (Apache, NCSA and some other web servers) and "ASP"; processing occurs at the time the documents are actually retrieved. A typical inclusion looks like  but be sure to consult your own server's documentation, as the details vary somewhat between implementations. The whole directive gets replaced by the contents of the specified file. Using server-side inclusion (a potentially powerful tool) merely as a way to insert static files such as standard header/footers has implications for perceived access speed and for server load, and is better avoided on heavily loaded servers. If you use it in this way, consider making the result cacheable (e.g., via "XBitHack full" on Apache; setting properties of the "Response" object in ASP). Details are beyond the scope of this FAQ but you may find this useful: http://www.pobox.com/~mnot/cache_docs/ Proper HTML validation of server-side inclusion is only possible after server-side processing is done, e.g. by using an on-line validator that retrieves the document from the server. 3.2. Which should I use, &entityname; or &#number; ? In HTML, characters can be represented in three ways: 1. a properly coded character, in the encoding specified by the "charset" attribute of the "Content-type:" header; 2. a character entity (&entityname;), from the appropriate HTML specification (HTML 2.0/3.2, HTML 4.0 etc.); 3. a numeric character reference (&#number;) that specifies the Unicode reference of the desired character. We recommend using decimal references; hexadecimal references are less widely supported. In theory these representations are equally valid. In practice, authoring convenience and limited support by browsers complicate the issue. HTTP being a guaranteed "8-bit clean" protocol, you can safely send out 8-bit o r multibyte coded characters, in the various codings that are supported by browsers. A. HTML 2.0/3.2 (Latin-1) By now there seems no convincing reason to choose &entityname; versus &#number; , so use whichever is convenient. If you can confidently handle 8-bit-coded characters this is fine too, probably preferred for writing heavily-accented languages. Take care if authoring on non-ISO-8859-based platforms such as Mac, Psion, IBM mainframes etc., that your upload technique delivers a correctly coded document to the server. Using &-representations avoids such problems. B. A single repertoire other than Latin-1 In such codings as ISO-8859-7 Greek, koi8-r Russian Cyrillic, and Chinese, Japanese and Korean (CJK) codings, use of coded characters is the most widely supported and used technique. Although not covered by HTML 3.2, browsers have supported this quite widely for some time now; it is a valid option within the HTML 4.0 specification--use a validator such as the WDG HTML Validator at http://www.htmlhelp.com/tools/validator/ which supports HTML 4.0 and understand s different character encodings. Browser support for coded characters may depend on configuration and font resources. In some cases, additional programs called "helpers" or "add-ins" supply virtual fonts to browsers. "Add-in" programs have in the past been used to support numeric references to 15-bit or 16-bit code protocols such as Chinese Big5 or Chinese GB2312. In theory you should be able to include not only coded characters but also Unicode numeric character references, but browser support is generally poor. Numeric references to the "charset-specified" encoding may appear to produce th e desired characters on some browsers, but this is wrong behavior and should not be used. Character entities are also problematical, aside from the HTML-significant characters <, & etc. C. Internationalization per HTML 4.0 Recent versions of the popular browsers have support for some of these features , but at time of writing it seems unwise to rely on this when authoring for a general audience. If you'd like to explore the options, you can find comprehensive background documentation and some practical suggestions at * http://www.czyborra.com/ * http://www.hut.fi/u/jkorpela/chars.html * http://ppewww.ph.gla.ac.uk/~flavell/charset/ 3.3. Should I use lower case or upper case for tags? Tags are case insensitive, so it doesn't matter. This is just a matter of style . (You may have noticed that this FAQ is not absolutely consistent in capitalization.) Many people prefer upper case, as it makes the tags "stand out " better amongst the text. Attribute names can also be upper or lower case, as you prefer. But some attribute values are case sensitive. For example, <OL TYPE=A> and <OL type=A> are the same, but <OL TYPE=a> is different from both of them. (For clearer communication, it's worth getting the terminology right. In this example, OL is the element, TYPE is the attribute name, and A and a are the attribute values. The tag is <OL TYPE=A>.) Entity names like are sometimes incorrectly referred to as tags. They ar e all case sensitive. For example, É and é are two different an d valid entities; &NBSP; is invalid. Note that XHTML 1.0 (a reformulation of HTML 4.0 as an XML 1.0 application) requires element and attribute names to be in lower case. 3.4. For what screen size should I write? HTML does not depend on screen size. Normally, the text will be wrapped by the browser when the end of its display area is encountered. (Note that graphical browsers are often used with windows that are smaller than the full area of the screen.) Preformatted lines (text within <PRE> elements) should only ever exceed 70 characters if the nature of the content makes it unavoidable. Longer lines will cause ugly line breaks on text-mode browsers, and will force horizontal scrolling on graphical browsers. Readers strongly dislike horizontal scrolling, except where they can realise that the nature of the content made it inevitable . Images cannot be wrapped, so you have to be careful with them. It seems that 40 0 or 500 pixels is a reasonable width; anything above 600 will mean a certain percentage of users will have to scroll to see the rightmost bit. This percentage increases with your image width. Keep in mind that not everyone runs his browser at full screen! (WebTV users have no ability to scroll horizontally, so anything beyond 544 pixels will be compressed by their browser. Some other devices may be even more limited.) 3.5. Why does my page display fine in browser X but incorrectly or not at all i n browser Y? There are several possibilities. First, you may have some incorrect HTML. Browsers vary in their ability to gues s what you meant. For instance, Netscape is much more fussy about tables than MS Internet Explorer, so a page with incorrect tables may look fine in MSIE but no t display at all in Netscape. See the answer to "How can I check for errors?" for tips on finding your HTML errors. (In fact, even correct nested tables may not display correctly in Netscape. See "Can I nest tables within tables?" below for what you can do about that.) Second, you may have valid HTML that different browsers interpret differently. For instance, it is not clear from the spec what should be done with a string o f characters. Some browsers will collapse them for rendering as a single space; others will render one space per . Third, your server may be sending incorrect MIME types for some of your files. Internet Explorer incorrectly ignores server-provided MIME types, so it sometimes "does the right thing" when the server is misconfigured. Other browsers correctly heed the server-provided MIME types, so they will reveal server misconfigurations. Other possibilities are a bug in one or the other browser, or different user option settings. See also the answers to "Why are my hyperlinks coming out all wrong or not loading?" and "Why are my images coming out all wrong or not loading?" 3.6. Why does the browser show my plain HTML source? If Microsoft Internet Explorer displays your document normally, but other browsers display your plain HTML source, then most likely your web server is sending the document with the MIME type "text/plain". Your web server needs to be configured to send that filename with the MIME type "text/html". See the answer to "Why did my link to a _______ file only download a bunch of character s instead?" for more details. 3.7. How do I freeze the URL displayed in a visitor's browser? This is a "feature" of using frames: The browser displays the URL of the frameset document, rather than that of the framed documents. (See the answer to the question "How do I specify a specific combination of frames instead of the default document?"). However, this behavior can be circumvented easily by the user. Many browsers allow the user to open links in their own windows, to bookmark the document in a specific frame (rather than the frameset document), or to bookmark links. Thus, there is no reliable way to stop a user from getting the URL of a specific document. Furthermore, preventing users from bookmarking specific documents can only antagonize them. A bookmark or link that doesn't find the desired document is useless, and probably will be ignored or deleted. 3.8. How do I make a table which looks good on non-supporting browsers? See Alan Flavell's document on tables for a good discussion at <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/www/tablejob.html>. 3.9. Can I nest tables within tables? Yes, a table can be embedded inside a cell in another table. Here's a simple example: <table> <tr> <td>this is the first cell of the outer table</td> <td>this is the second cell of the outer table, with the inner table embedded in it<br> <table> <tr> <td>this is the first cell of the inner table</td> <td>this is the second cell of the inner table</td> </tr> </table> </td> </tr> </table> The main caveat about nested tables is that Netscape has problems with them if you don't close your TD and TR tags meticulously. You're best advised to includ e every </TD> and </TR>, even though the HTML spec doesn't require them; otherwis e Netscape users may not be able to view your page. 3.10. How do I center a table? The "correct" way of doing it is <TABLE ALIGN=CENTER>, but this doesn't work in several popular browsers. Put <CENTER>; around the entire table for these browsers. This causes some problems with browsers that do support CENTER but not tables, such as Lynx. In these browsers, the contents of the cells are now displayed centered, which is not what is intended. To avoid this, you can put the cell's contents in <P ALIGN=left> or <DIV ALIGN=left> depending on the amount of text in the cell. 3.11. Can I use percentage values for <TD WIDTH=...>? The HTML 3.2 and HTML 4.0 specifications allow only integer values (representin g a number of pixels) for the WIDTH attribute of the TD element. However, the HTM L 4.0 DTD allows percentage (and other non-integer) values, so an HTML validator will not complain about <TD WIDTH="xx%">. It should be noted that Netscape and Microsoft's browsers interpret percentage values for <TD WIDTH=...> differently. However, their interpretations (and thos e of other table-aware browsers) happen to match when combined with <TABLE WIDTH="100%">. In such situations, percentage values can be used relatively safely, even though they are prohibited by the public specifications. 4. Hyperlinks 4.1. Should I end my URLs with a slash? The trailing slash is used to distinguish between directory and file URLs. A file URL is an URL for a file, and a directory URL refers to a directory. For example, the URL for the WDG's HTML reference is http://www.htmlhelp.com/reference/ and the URL for the overview of HTML 3.2 elements is http://www.htmlhelp.com/reference/wilbur/overview.html If you request a directory URL without the trailing slash, the browser will actually ask for a FILE with that name. This file doesn't exist on the server, so the server sends back a message saying that the browser should ask for the directory. It uses a redirection message for this. The browser then sends another request, this time for the directory, and finally gets what was asked for in the first place. This wastes time and network resources. When you write a document, all directory URLs should end with a slash. Since yo u already know you are linking to a directory, why force the user to make that second request, when it could have been done using only one? And by the way, it is NOT the browser which appends the slash. The browser cannot know if what you are asking for is a file or directory, not even when th e final part of the URL does not have an extension. http://www.somewhere.com/src/something/README is a perfectly valid URL, has no extension in the final part, yet refers to a file and not a directory. The only apparent exception is when you refer to an URL with just a hostname. Since it is obvious that when you use http://www.htmlhelp.com you actually want the main index "/" from our server, you do not have to include the / in this case. It is regarded as good style to do so, however. For a full discussion of the proper form of URLs, see RFC 1738 at <URL:http://www.cis.ohio-state.edu/htbin/rfc/rfc1738.html> and, for relative URLs, RFC 1808 at <URL:http://www.cis.ohio-state.edu/htbin/rfc/rfc1808.html>. 4.2. How do I link to a location in the middle of an HTML document? First, identify the destination of the link with a named anchor (an anchor that uses the NAME attribute). For example: <H2><A NAME="section2">Section 2: Beyond Introductions</A></H2> Second, link to the named anchor. The URL of the named anchor is the URL of the document, with "#" and the name of the anchor appended. For example, elsewhere in the same document you could use: <A HREF="#section2">go to Section 2</A> Similarly, in another document you could use: <A HREF="thesis.html#section2">go to Section 2 of my thesis</A> 4.3. How do I link without using the full URL? Links that do not specify the full URL are called relative links. Before the browser can request the linked document, it must generate the full URL using th e relative URL and the URL of the current document. First, the browser strips everything after the last slash ("/") in the URL of the current document. Second, it moves up one level in the URL hierarchy for each "../" at the beginning of the relative URL, removing the leading "../" strings from the relative URL as it does so. Third, it appends the relative URL to get the final URL. Some examples may help make this clear. Assuming that the current document is <URL:http://www.htmlhelp.com/faq/html/links.html>: "all.html" refers to <URL:http://www.htmlhelp.com/faq/html/all.html> "../" refers to <URL:http://www.htmlhelp.com/faq/> "../cgifaq.html" refers to <URL:http://www.htmlhelp.com/faq/cgifaq.html> "../../reference/" refers to <URL:http://www.htmlhelp.com/reference/> For more details on using and resolving relative URLs, see "Using Relative URLs " <URL:http://www.stack.nl/%7Egalactus/html/urls.html. 4.4. How do I create a link that opens a new window? <A TARGET="_blank" HREF=...> opens a new, unnamed window. <A TARGET="foobar" HREF=...> opens a new window named "foobar", provided that a window or frame by that name does not already exist. Note that links that open new windows can be annoying to your readers if there is not a good reason (from the reader's perspective) for them. 4.5. How do I create a link that opens a new window of a specific size? With HTML, there is no way to control the size (or window decoration, or other features) of a new window. However, in JavaScript you can specify such details when using the window.open() function. Start with a normal HTML link (possibly one that opens in a new window as described in the answer to the previous question). Then use the ONCLICK attribute to open a window with the desired appearance for those readers with JavaScript supported and enabled. The following example specifies a window name d "popup" that is 300 pixels by 150 pixels. <A HREF="foo.html" TARGET="popup" ONCLICK="window.open('foo.html', 'popup', 'width=300,height=150'); return false">View Foo</A> Used in this manner, JavaScript can specify a new window with the desired appearance, without blocking access when JavaScript is unsupported/disabled. 4.6. How do I get a button which takes me to a new page? This is best done with a small form: <FORM ACTION="http://url.you.want.to.go.to/" METHOD=GET> <INPUT TYPE=submit VALUE="Text on button" NAME=foo> </FORM> If you want to line up buttons next to each other, you will have to put them in a one-row table, with each button in a separate cell. Note that search engines might not find the target document unless there is a normal link somewhere else on the page. A go-to-other-page button can also be coded in JavaScript, but the above is standard HTML and works for more readers. 4.7. How do I get a back button on my page? In HTML, this is impossible. Going "back" means that you go to the previous pag e in your history. You might be able to create a link to the URL specified in the "HTTP_REFERER" environment variable in your document, but that only creates a link to a new location in your history. Even worse, the information in that variable can be plain wrong. Some browsers incorrectly send the variable when you use a bookmark or type in an URL manually, and some don't send that variabl e at all. This would result in an empty link. A JavaScript could use "history.back()" to do this, but this only works in Netscape 2 or higher and MSIE 3 or higher, and even then only if the user has not disabled JavaScript. For a more detailed explanation, please see Abigail's "Simulating the back button" at <URL:http://www.foad.org/%7Eabigail/HTML/Misc/back_button.html>. 4.8. How do I create a link that sends me email? Use a mailto: link, for example Send me email at <A HREF="mailto:me@mydomain.com">me@mydomain.com</A>. 4.9. How do I specify a subject for a mailto: link? You can't, not in any reliable way. The methods that are frequently posted don' t do the job on all browsers (or even all popular browsers), and many of them hav e an important drawback: if your visitors are using an older browser such as Netscape 1.22, their mail will be lost. If you really need a subject, you can do it by providing a form on your page, which submits data to a CGI program that emails the form data to you with your desired subject line. However, the form must have an input field for the visitor's email address, and you must hope that the visitor enters it correctly . Here are some other ways to transmit subject-type information: * Create email aliases that are used only for certain mailto links, so you'll know that anything sent to a given alias is in response to the correspondin g Web page(s). * The mail handlers for many Web browsers include an "X-Url" header that specifies the URL of the Web page that contained the mailto link. If you configure your mail reader to display this header, you'll see which Web pag e the sender is responding to much of the time. * Use <A HREF="mailto:user@site" TITLE="Your Subject">. Most browsers will ignore the TITLE attribute, but some minor browsers will use it as a subjec t for the email message. All browsers will send the mail. * Use <A HREF="mailto:user@site?subject=Your%20Subject">, which puts "Your Subject" (the space is encoded as "%20") in the "Subject" header field of the email message in most current browsers. The details of this recent RFC can be found at <URL:http://info.internet.isi.edu/in-notes/rfc/files/rfc2368.txt>. Note however that you will lose mail from users of older browsers, so you should consider whether the pre-filled subject is worth lost mail. 4.10. How do I link an image to something? Just use the image as the link content, like this: <A HREF=...><IMG ...></A> 4.11. How do I eliminate the blue border around linked images? Use the BORDER="0" attribute in the <IMG> element. For example: <A HREF="doc.html"><IMG SRC="doc.gif" ALT="View document." BORDER="0"></A> 4.12. How do I link different parts of an image to different things? Use an image map. Client-side image maps don't require server-side processing, so response time is faster. Server-side image maps hide the link definitions from the browser, and can act as a backup for client-side image maps for the fe w very old browsers that support server-side image maps but not client-side image maps. The configuration details of server-side image maps vary from server to server. Refer to your server documentation for details. Client-side image maps are implemented with HTML. The MAP element defines an individual image map and the AREA element defines specific linked areas within that image map. The USEMAP attribute of the IMG element associates an image map with a specific image. A detailed explanation (with examples) is available at <http://www.htmlhelp.com/reference/html40/special/map.html>. A tutorial is available at <http://ppewww.ph.gla.ac.uk/~flavell/www/imgmaptut.html>. 4.13. How do I turn off underlining on my links? If you want to turn off link underlining when you're looking at pages in your browser, check your browser's configuration options. In Netscape 3, for example , see Options | General Preferences | Appearance; in Netscape 4 it's Edit | Preferences | Appearance | Colors; in Internet Explorer see View | Options | General. If you want to prevent links on your page being underlined when your visitors see them, there's no way in HTML to accomplish this. You can suggest this presentation using style sheets by defining a:link, a:visited, a:active {text-decoration: none} 4.14. How can I have two sets of links with different colors? You can suggest this presentation using style sheets. In your style sheet, define something like this: a:link {color: blue; background: white} a:visited {color: purple; background: white} a:active {color: red; background: white} a.foo:link {color: yellow; background: black} a.foo:visited {color: white; background: black} a.foo:active {color: red; background: black} Then use CLASS="foo" to identify the links of the second color in your HTML, like this: <A CLASS="foo" HREF=...>...</A> 4.15. How can I make links change when the cursor is over them? In your style sheet, use the hover pseudo-class to specify a different appearance for links when the cursor is over them. Specify the hover pseudo-class after the link and visited pseudo-classes. For example: A:link { color: blue ; background: white } A:visited { color: purple ; background: white } A:hover { color: red ; background: white } 4.16. Why are my hyperlinks coming out all wrong or not loading? Most likely you forgot to close a quote at the end of the HREF attribute. Alternatively, perhaps you used a ">" character somewhere else inside a tag. Although this is legal, several older browsers will think the tag ends there, s o the rest is displayed as normal text. This especially happens if you use comment tags to "comment out" text with HTML tags. (See the answer to "How can I include comments in HTML?") Although the correct syntax is  (without "--" occurring anywhere inside the comment) , some browsers will think the comment ends at the first ">" they see. Validators will show you any syntax errors in your markup, but checkers such as Weblint and HTMLchek can show you where you are liable to provoke known browser bugs. See also the answer to "How can I check for errors?" 4.17. Why does my link work in Internet Explorer but not in Netscape? Is there a space, #, ?, or other special character in the path or filename? Spaces are not legal in URLs. If you encode the space by replacing it with %20, your link will work. You can encode any character in a URL as % plus the two-digit hex value of the character. (Hex digits A-F can be in upper or lower case.) According to the spec, only alphanumerics and the special characters $-_.,+!*'() need not be encoded. You should encode all other characters when they occur in a URL, except when they're used for their reserved purposes. For example, if you wanted to pass th e value "Jack&Jill" to a CGI script, you would need to encode the "&" character a s "%26", which might give you a URL like the following: http://www.foo.com/foo.cgi?rhyme=Jack%26Jill&audience=child. Note that the "?" and other "&" character in this URL are not encoded since they're used for thei r reserved purposes. See section 2.2 of RFC 1738 at <URL:http://www.w3.org/Addressing/rfc1738.txt> for the full story. 5. Other Media 5.1. How do I let people download a file from my page? Once the file is uploaded to the server, you need only use an anchor reference tag to link to it. An example would be: <a href="../files/foo.zip">Download Foo Now! (100kb ZIP)</a> It is possible that the server might need to be configured for some different file types. (See the next Q&A.) 5.2. Why did my link to a _______ file only download a bunch of characters instead? If you are trying to link to a particular type of file and it is not returning your desired response, chances are that the server needs to have the type configured. Talk to your system administrator about getting them to add the content type. Here is a list of common types that often need configuring: Content Type Description Application/msword Microsoft Word Document application/octet-stream Unclassified binary data (often used for compressed file or executable) application/pdf PDF Document application/wordperfect6.0 WordPerfect 6.0 Document application/zip ZIP archive audio/x-wav WAV audio format audio/midi MIDI audio format audio/x-pn-realaudio RealAudio image/gif GIF image format image/jpeg JPEG image format image/png PNG image format text/html HTML document text/plain Plain text video/mpeg MPEG video format video/quicktime QuickTime video format video/x-msvideo AVI video format Another method of ensuring that your file is properly sent to the client is to compress it into a standard compression format. Virtually all servers are set t o handle the .zip extension and it is widely recognized by users. Some servers (NCSA, Apache, and others) can be configured to support user-configured content types. Details are server dependent, so consult your server admin or documentation. Note that Internet Explorer incorrectly ignores server-provided MIME types, so it sometimes "does the right thing" when the server is misconfigured. Other browsers correctly heed the server-provided MIME types, so they will reveal server misconfigurations. 5.3. How do I force a download? You can't, because the Web doesn't work that way. Here's the explanation. When someone downloads a document, the server tells the browser what type of file it is. The browser then displays it or picks the appropriate helper application. If the server doesn't know the file type, it tells the browser that the file is "text/plain", or just plain text (true for most servers). You may need to ask your server admin to configure this particular file with the MIME type you want. "Forcing" a download is not what you are supposed to do. After all, what is mor e convenient than having the proper application started when I download a particular file? Browsing through a download directory can be quite a pain. And most browsers allow the user to download to disk if they want to. If the file must be saved to disk, if there is absolutely NO other way to handl e it, the MIME type should be "application/octet-stream". 5.4. How do I make animated GIFs? Check out the following resources: * http://members.aol.com/royalef/gifanim.htm * http://www.adobe.com/studio/tipstechniques/GIFanimation/main.html * http://www.webreference.com/dev/gifanim/ 5.5. How can I create a thumbnail image that is linked to the full-sized image? A thumbnail image is just a copy of the full-sized image that has been modified to reduce the size of the file. It is linked to the full-sized image with a normal link: <A HREF="full-sized.jpg"><IMG SRC="thumbnail.jpg" ALT=...></A> There are several techniques for reducing the size of the file for the thumbnai l image, including * resampling/resizing the image to create a physically smaller image; * cropping the image to remove less significant parts of the image; * reducing the image quality to increase compression ratios; and * reducing the size of the color palette (e.g., converting to greyscale). Thumbnail images can use multiple techniques simultaneously. For example, Jakob Nielsen advocates "Relevance-Enhanced Image Reduction", which combines resampling/resizing and cropping. 5.6. Why am I getting a colored whisker to the left or right of my image? This is the result of including "white space" (spaces and newlines) before or after an IMG inside an anchor. For example: <A HREF=...> <IMG SRC=...> </A> will have white space to the left and right of the image. Since many browsers display anchors with colored underscores by default, they will show the spaces to the left and right of the image with colored underscores. Solution: don't leave any white space between the anchor tags and the IMG tag. If the line gets too long, break it inside the tag rather than outside it, like this: <A HREF=...><IMG SRC=...></A> Style checkers such as Weblint will call attention to this problem in your HTML source. 5.7. How can I display random images? There are two basic approaches. The most cache-friendly method is to use a normal IMG tag that refers to a CGI script that randomly redirects the browser to one of several images. There is an example of such a CGI script at <URL:http://www.foad.org/%7Eabigail/CGI/random_images.html>. See the CGI Programming FAQ <URL:http://www.htmlhelp.com/faq/cgifaq.html> for more information about CGI. The second method is to generate the HTML dynamically using a mechanism like Server Side Includes (SSI) or CGI. This method is less cache-friendly, but it does allow the surrounding markup (e.g., HEIGHT and WIDTH attributes, or the URLs for linked/image-mapped images) to vary with the image. If your server supports SSI, the details can be found in your server documentation. 5.8. Why are my images coming out all wrong or not loading? Most likely you forgot to close a quote at the end of the SRC attribute. Alternatively, perhaps you used a ">" character in an ALT text or somewhere els e inside a tag. Although this is legal, several older browsers will think the tag ends there, so the rest is displayed as normal text. This especially happens if you use comment tags to "comment out" text with HTML tags. (See the answer to "How can I include comments in HTML?") Although the correct syntax is  (without "--" occurring anywhere inside the comment) , some browsers will think the comment ends at the first ">" they see. Validators will show you any syntax errors in your markup, but checkers such as Weblint and HTMLchek can show you where you are liable to provoke known browser bugs. See also the answer to "How can I check for errors?" 5.9. How do I prevent people from saving my images? You can't. The image file is necessary for the browser to display your document ; you must send it to the browser. Even if a particular browser doesn't have a "Save Image" feature, there are many that do, and someone can always retrieve the image file by hand (using telnet) or from the browser's cache. There are tricks that make it more difficult for some readers to save your images. However, just as with tricks that try to hide HTML source, these tricks cause various problems for law-abiding users and can't really prevent thieves from saving your images. 5.10. Can I put markup in ALT text? No. Character entities (©, &#nnn; and such) are permitted, though. If you want to know how to write good ALT texts without markup, please see Alan Flavell's essay on choosing ALT texts at <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/alt/alt-text.html>. 5.11. How do I get an audio file to play automatically when someone visits my site? Most browsers support the EMBED element for this, provided that the user has a suitable plug-in for the sound file. You can reach a slightly wider audience if you use BGSOUND as well. To avoid problems with browsers that support both, place the BGSOUND in a NOEMBED container: <EMBED SRC="your_sound_file" HIDDEN=true AUTOSTART=true> <NOEMBED><BGSOUND SRC="your_sound_file"></NOEMBED> For more on the EMBED element, see <URL:http://developer.netscape.com/docs/manuals/htmlguid/tags14.htm#1286379>. See <URL:http://msdn.microsoft.com/developer/sdk/inetsdk/help/dhtml/references/html /BGSOUND.htm> for more information on BGSOUND. Note that these elements are proprietary and not in any HTML standard. (The HTML standard way of doing this is not well supported.) Be aware that some users find it annoying for music to automatically start playing. They may not have the volume set properly on their speakers, or they may be listening to something else. As a courtesy to your users, you may prefer to offer the sound file as a link: <A HREF="your_sound_file">Listen to my sound! (5 kB MIDI)</A> 5.12. How can I strip all the HTML from a document to get plain text? Many browsers have a "Save As..." function that allows you to specify plain tex t as the output format. Another approach is to select all the text, copy it to th e clipboard, and paste it into an editor. Lynx users can use "lynx -dump http://..." on the command line to print to file and append a list of referenced URLs as footnotes. If you want the output file without the footnotes, use the "p" command to "print" to a text file. Some HTML authoring tools have an option to strip all HTML as well. Two program s of note are * HomeSite, available from <URL:http://www.allaire.com/> * DiDa, available from <URL:http://www.faico.net/> If you are looking for another method (in other words you want to make things more difficult on yourself), you can obtain programs which will strip away all HTML markup from a document. Try doing a search at <URL:http://www.altavista.com/> for the phrase "HTML stripper". 6. Presentational Effects 6.1. How can I make a custom rule? Your best option is likely a centered IMG with a line of "--" characters as ALT text: <P ALIGN=center><IMG SRC="custom-line.gif" ALT="--------------------"></P> For an experimental but somewhat more graceful approach, read about CSS1 and th e Decorative HR at <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/www/hrstyle.html>. 6.2. How can I make a list with custom bullets? There are several methods, none completely satisfactory: * Use the list-style property of Cascading Style Sheets. This should be the preferred method of using custom bullets, but unfortunately it's not widely supported by browsers. However, non-supporting browsers will see a normal bullet, so using this method today is not a problem. See <URL:http://www.htmlhelp.com/reference/css/> for more information on style sheets. * Use a <DL> with <DD> tags with preceding images (with ALIGN and suitable AL T text) and no <DT>; this won't be as beautiful as a "real" list. * Use a two-column table, with the bullets in the left column and the text in the right. Since browsers show nothing before downloading the entire table, this can be slow with long lists. * Create the bullet with the indent built in. For example, if you use a bulle t that is 10 pixels across you can make the background 25 pixels (transparent ) and put the bullet all the way on the right. This will create a 15-pixel indent to the left of the bullet. It will add slightly to the byte size of the graphic but since it is all one color it won't add much. This method doesn't work well with any list items that are longer than a line (and remember that you don't know how long a line will be on the visitor's screen). 6.3. Where can I get a "hit counter"? A hit counter is a small script or program that increases a number every time a document is accessed from the server. Why do you want one? If you believe that it will tell you how many times your documents have been accessed, you are mistaken. No counter can keep track of accesses from browser caches or proxy caches. Some counters depend on image-loading to increment; such counters ignore accesses from text-mode browsers, or browsers with image-loading off, or from users who interrupted the transfer. Some counters even require access to a remote site, which may be down or overloaded, causing a delay in displaying your documents. Most web servers log accesses to documents stored on the server machine. These logs may be processed to gain information about the *relative* number of accesses over an extended period. There is no reason to display this number to your viewers, since they have no reference point to relate this number to. Not all service providers allow access to server logs, but many have scripts that will output information about accesses to a given user's documents. Consult you r sysadmin or service provider for details. Counter services and information are available from Yahoo's list of counters: http://www.yahoo.com/Computers/World_Wide_Web/Programming/Access_Counts/ Log analysis tools and scripts are at http://www.yahoo.com/Business_and_Economy/Companies/Computers/Software/Internet /World_Wide_Web/Log_Analysis_Tools/ <URL:http://www.markwelch.com/bannerad/baf_counter.htm> is another good source for counter information. A discussion of the limitations of web-traffic statistics is at <URL:http://www.cranfield.ac.uk/docs/stats/> 6.4. How do I display the current date or time in my document? With server-side includes. Ask your webmaster if this is supported, and what th e exact syntax is for your server. But this will display the local time on the server, not for the client. And if the document is cached, the date will of course be incorrect after some time. JavaScript can be used to display the loca l time for the client, but again, as most people already have one or more clocks on their screen, why display another one? If you plan on putting the current date or time on your pages, using a CGI, JavaScript or VBScript, take an extra breath and consider that it will take resources, add time to the loading of the page, and prevent good caching. If yo u find that you really have a need to use it, for instance to inform readers of the up-times of an FTP server, then by all means do so. If, on the other hand, your only reason is 'it looks cool!' - then reconsider. 6.5. How do I get scrolling text in the status bar? This is not an HTML question; it's done with JavaScript. Check any page which has this feature, and copy the script from the source. This script has two big problems. One, usually it uses the decrement operator (c--) at some point. The "--" sequence in a comment actually closes it on some browsers, so your code may "leak" on those browsers. The same goes for ">". Second, keep in mind that many people consider this even worse than <BLINK>, an d that it also suppresses the status information which normally appears there. It prevents people from knowing where a link goes to. 6.6. How do I right align text or images? You can use the ALIGN=right attribute on paragraphs, divisions, and headers, just as you use ALIGN=center to create centered paragraphs and such. This will right align your text (ragged left). Perhaps what you really want is justified text, in which the left and right edges are both aligned so that all lines are the same length. (This is sometime s incorrectly called "right justify".) There's no way to justify text in HTML 3.2 , but it can be done in a CSS1 style sheet with "text-align: justify". (Before yo u do that, a caveat: though justified text may look pretty, human factors analysi s shows that ragged right is actually easier to read and understand.) For images, you can use <IMG ALIGN=right SRC="..." ALT="..."> before the runnin g text. The image will float at the right margin, and the running text will flow around it. Remember to use <BR CLEAR=right> or <BR CLEAR=all> to mark the end o f the text that is to be affected in this way. 6.7. How can I specify fonts in my Web pages? If you want others to view your web page with a specific font, the most appropriate way is to suggest the font rendering with a style sheet. See: http://www.htmlhelp.com/reference/css/font/font-family.html The FONT element can also be used to suggest a specific font. Use of the FONT element brings numerous usability and accessibility problems, see: http://www.mcsr.olemiss.edu/%7Emudws/font.html More information about the FONT element can be found at: http://www.htmlhelp.com/reference/html40/special/font.html Either way, authors run the risk that a reader's system has a font by the same name but which is significantly different. (e.g., "Chicago" can be a nice text font, or a display font with letters formed by "bullet holes", or a dingbat fon t with building images for creating skylines). Also, authors are limited to choosing a font (or a group of similar fonts) that are commonly available on many systems. If a reader does not have the font installed on their system, they will see a default font. Some browsers may use a less legible substitute font than their normal default font in cases where "the specified font wasn't found". 6.8. How do I indent the first line in my paragraphs? Use a style sheet with the following ruleset: P { text-indent: 5% } See <URL:http://www.htmlhelp.com/reference/css/> for more information on style sheets. 6.9. How do I indent a lot of text? Use a style sheet to set a left margin for the whole document or part of it: /* Entire document */ BODY { margin-left: 20% } /* Part of a document with CLASS="foo" */ .foo { margin-left: 15% } See <URL:http://www.htmlhelp.com/reference/css/> for more information on style sheets. 6.10. How do I do a page break? Page breaks are offered in Cascading Style Sheets, Level 2, but they are not well supported by browsers. See <URL:http://www.w3.org/TR/REC-CSS2/page.html#page-breaks> for information on CSS2 page breaks. In general, page breaks are not appropriate on the Web since what makes a nice page break for you with your font and font size may be a poor page break for me with my font and font size. If you need to produce a nicely formatted printed copy of your HTML documents, you might also consider using special purpose tools rather than your browser's Print function. For example, html2ps generates nicely formatted PostScript output from HTML documents, and HTML Scissor uses special HTML comments for suggesting page breaks. 6.11. How do I have a fixed background image? Use a style sheet with the following ruleset: body { color: black; background: white url(foo.gif) fixed } Note that the fixed property used in the above style sheet is supported by Internet Explorer 3+, Netscape Navigator 5+, and other browsers. In contrast, the proprietary BGPROPERTIES=fixed attribute is supported only by Internet Explorer 3+. 6.12. How do I have a non-tiled background image? Use a style sheet with the following ruleset: body { color: black; background: white url(foo.gif) no-repeat } 6.13. How can I have a custom icon when people bookmark my site? This is a feature introduced by Internet Explorer 5.x. By default, the browser requests an file named "favicon.ico" at the same base URL as the document being bookmarked. If it doesn't find this file, then it will try again in the root directory of your site. Web authors can specify a different path for the icon file with a <LINK> element like this: <LINK REL="SHORTCUT ICON" HREF="/pathname/filename.ico"> The image should be 16 by 16 pixels, in the Windows icon format. If your graphics program doesn't support the Windows icon format, you can use a tool like the free Java-based icon generator at <URL:http://www.favicon.com/> to convert/create your icon. For further information, search for "favicon.ico" at <URL:http://msdn.microsoft.com/workshop/essentials/versions/ICPIE5.asp>. 7. HTML Forms 7.1. How do I use forms? The basic syntax for a form is: <FORM ACTION="[URL]">...</FORM> When the form is submitted, the form data is sent to the URL specified in the ACTION attribute. This URL should refer to a server-side (e.g., CGI) program that will process the form data. The form itself should contain * at least one submit button (i.e., an <INPUT TYPE="submit" ...> element), * form data elements (e.g., <INPUT>, <TEXTAREA>, and <SELECT>) as needed, and * additional markup (e.g., identifying data elements, presenting instructions ) as needed. A more detailed explanation of the use of forms is available at <URL:http://www.hut.fi/u/jkorpela/forms/>. If you want to install CGI programs on your server, the following are useful resources: * the CGI Programming FAQ <URL:http://www.htmlhelp.com/faq/cgifaq.html> * the CGI section of the W3C's Security FAQ <URL:http://www.w3.org/Security/faq/wwwsf4.html> * the list of prewritten CGI scripts/programs at <URL:http://www.cgi-resources.com/Programs_and_Scripts/> 7.2. How do I get form data emailed to me? The only reliable mechanism for processing form submissions is with a server-side (e.g., CGI) program. To send form data to yourself via email, you should use a server-side program that processes the form submission and sends the data to your email address. Some web service providers make standard form-to-email programs available to their customers. Check with your service provider for details. If you can install CGI programs on your own server, see the answer to the previous question for a list of useful resources. If you can't run CGI programs on your own server, you can use a remotely hosted form-to-email services. A list of such services can be found at <URL:http://www.cgi-resources.com/Programs_and_Scripts/Remotely_Hosted/Form_Pro cessing/>. Note that the provider of a remotely hosted service will have access to any dat a submitted via the service. Forms that use ACTION="mailto:..." are unreliable. They may work for some of your users, but they will fail for others who have different software configurations. 7.3. How do I make a form so it can be submitted by hitting ENTER? The short answer is that the form should just have one <INPUT TYPE=TEXT> and no TEXTAREA, though it can have other form elements like checkboxes and radio buttons. For a more detailed answer, see <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/www/formquestion.html>. 7.4. How can I make a form with custom buttons? Rather than a normal submit button (<INPUT TYPE=submit ...>), you can use an image of a custom submit button. Use <INPUT NAME=Send TYPE=image SRC="http://url.to/image.gif" ALT="Send" VALUE="Send">. Most browsers will also send the x and y coordinates of the location where the user clicked on the imag e to the server. They are available as "Send.x=000&Send.y=000" in the CGI input. For more information, see <URL: http://ppewww.ph.gla.ac.uk/%7eflavell/www/trysub.html>. For the reset button, one could use <BUTTON TYPE=reset ...>, JavaScript, and/or style sheets, although none of these mechanisms work universally. For more information, see <URL:http://www.hut.fi/u/jkorpela/forms/imagereset.html>. 7.5. Can I have two or more Submit buttons in the same form? Sure. This is part of HTML 2.0 Forms support (some early browsers did not support it, but browser coverage is now excellent). You will need to give your Submit buttons a Name attribute, and, optionally, a Value attribute. In order to determine which button was used, you will want to use distinctive Names, or Values, or both. Browsers will display the Value, in addition to sending it to the server, so choose something that's meaningful to the user. Example: <INPUT TYPE=SUBMIT NAME=join VALUE="I want to join now"> -or- <INPUT TYPE=SUBMIT NAME=info VALUE="Please send full details"> If you're unsure what results you're going to get when you submit your form, NCSA has a standard script which you can use. Code this, for example (assuming method "post"): <form method="post" action="http://hoohoo.ncsa.uiuc.edu/htbin-post/post-query"> and then go through the motions of submitting your form. The NCSA server decode s the form input, and displays the result to you. 7.6. How can I allow file uploads to my web site? First of all, the RFC for this is located at <URL:http://www.ics.uci.edu/pub/ietf/html/rfc1867.txt>. File upload is handled by the CGI.pm Perl5 library available from <URL:http://stein.cshl.org/WWW/software/CGI/cgi_docs.html>. The most recent versions of the cgi-lib.pl library also support file upload. These things are necessary for Web-based uploads: * An HTTP server that accepts uploads. * Access to the /cgi-bin/ to put the receiving script. * A form implemented something like this: <form method="POST" enctype="multipart/form-data" action="fup.cgi"> File to upload: <input type=file name=upfile><br> Notes about the file: <input type=text name=note><br> <input type=submit value=Press> to upload the file! </form> Not all browsers support form-based file upload, so try to give alternatives where possible. Also, if you need to do file upload in conjunction with form-to-email, the Perl package MIME::Lite handles email attachments. 7.7. How can I use forms for pull-down navigation menus? There is no way to do this in HTML only; something else must process the form. JavaScript processing will work only for readers with JavaScript-enabled browsers. CGI and other server-side processing is reliable for human readers, but search engines have problems following any form-based navigation. See <http://www.hut.fi/u/jkorpela/forms/navmenu.html>, which explains how to create pull-down menus, as well as some better navigation alternatives. 8. HTML Frames 8.1. How do I make a link or form in one frame update another frame? In the frameset document (the HTML document containing the <FRAMESET> and <FRAME> elements), make sure to name the individual frames using the NAME attribute. The following example creates a top frame named "navigation" and a bottom frame named "content": <FRAMESET ROWS="*,3*"> <FRAME NAME="navigation" SRC="navigation.html"> <FRAME NAME="content" SRC="content.html"> <NOFRAMES><BODY>  </BODY></NOFRAMES> </FRAMESET> Then, in the document with the link, use the TARGET attribute to specify which frame should be used to display the link. (The value of the TARGET attribute should match the value of the target frame's NAME attribute.) You can specify the target frame for a link (e.g., <A TARGET="content" HREF=...>) or for a form (e.g., <FORM TARGET="content" ACTION=...>). Also, you can use <BASE TARGET=...> to change the default target frame for the entire document (normally, the default target frame is "_self", the current frame). 8.2. Why do my links open new windows rather than update an existing frame? If there is no existing frame with the name you used for the TARGET attribute, then a new browser window will be opened, and this window will be assigned the name you used. Furthermore, TARGET="_blank" will open a new, unnamed browser window. In HTML 4.0, the TARGET attribute value is case-insensitive, so that abc and AB C both refer to the same frame/window, and _top and _TOP both have the same meaning. However, most browsers treat the TARGET attribute value as case-sensitive and do not recognize ABC as being the same as abc, or _TOP as having the special meaning of _top. 8.3. How do I update two frames at once? There are two basic techniques for updating multiple frames with a single link: The HTML-based technique links to a new frameset document that specifies the ne w combination of frames. The JavaScript-based solution uses the onClick attribute of the link to update the additional frame (or frames). The HTML-based technique can link to a new frameset document with TARGET="_top" (replacing the entire frameset), but there is an alternative if the frames to b e updated are part of a nested frameset. In the initial frameset document, use a secondary frameset document to define the nested frameset. For example: <FRAMESET COLS="*,3*"> <FRAME SRC="contents.html" NAME="Contents"> <FRAME SRC="frameset2.html" NAME="Display"> </FRAMESET> A link can now use TARGET="Display" to replace simultaneously all the frames defined by frameset2.html. The JavaScript-based solution uses the onClick attribute of the link to perform the secondary update. For example: <A HREF="URL1" TARGET=Frame1 onClick="top.Frame2.location='URL2';">Update frames</A> The link will update Frame1 with URL1 normally. If the reader's browser support s JavaScript (and has it enabled), then Frame2 will also be updated (with URL2). 8.4. How do I get out of a frameset? If you are the author, this is easy. You only have to add the TARGET attribute to the link that takes readers to the intended 'outside' document. Give it the value of _top. In many current browsers, it is not possible to display a frame in the full browser window, at least not very easily. The reader would need to copy the URL of the desired frame and then request that URL manually. I would recommend that authors who want to offer readers this option add a link to the document itself in the document, with the TARGET attribute set to _top s o the document displays in the full window if the link is followed. 8.5. How do I make sure my framed documents are displayed inside their frameset ? When the sub-documents of a frameset state are accessed directly, they appear without the context of the surrounding frameset. If the reader's browser has JavaScript support enabled, the following script will restore the frameset: <SCRIPT TYPE="text/javascript">  </SCRIPT> A more universal approach is a "restore frames" link: <A HREF="frameset.html" TARGET="_top">Restore Frames</A> Note that in either case, you must have a separate frameset document for every content document. If you link to the default frameset document, then your reade r will get the default content document, rather than the content document he/she was trying to access. These frameset documents should be generated automatically, to avoid the tedium and inaccuracy of creating them by hand. Note that you can work around the problem with bookmarking frameset states by linking to these separate frameset documents using TARGET="_top", rather than linking to the individual content documents. 8.6. Is there a way to prevent getting framed? "Getting framed" refers to having your documents displayed within someone else' s frameset without your permission. This can happen accidentally (the frameset author forgot to use TARGET="_top" when linking to your document) or intentionally (the frameset author wanted to display your content with his/her own navigation or banner frames). To avoid "framing" other people's documents, you must add TARGET="_top" to all links that lead to documents outside your intended scope. Unfortunately, there is no reliable way to specify that a particular document should be displayed in the full browser window, rather than in the current frame. If you can configure your server to send the proprietary header Window-Target: _top in the HTTP response, then Netscape browsers will display your document in the full browser window. However, other browsers ignore this header, and it doesn't work to use <META HTTP-EQUIV="Window-target" CONTENT="_top"> in the document itself to mimic the HTTP response. Another workaround is to use <BASE TARGET="_top"> in the document, but this onl y specifies the default target frame for links in the current document, not for the document itself. If the reader's browser has JavaScript enabled, the following script will automatically remove any existing framesets: <SCRIPT TYPE="text/javascript">  </SCRIPT> An alternative script is <SCRIPT TYPE="text/javascript">  </SCRIPT> </HEAD> <BODY onLoad="breakOut()"> 8.7. How do I specify a specific combination of frames instead of the default document? This is unfortunately not possible. When you navigate through a site using frames, the URL will not change as the documents in the individual frames change. This means that there is no way to indicate the combination of document s that make up the current state of the frameset. The author can provide and link to multiple frameset documents, one for each combination of frame content. These frameset documents can be generated automatically, possibly even being created on the fly by a CGI program. 8.8. How do I remove the border around frames? Removing the border around frames involves both not drawing the frame borders and eliminating the space between the frames. The two major frames-capable browsers use different proprietary attributes to achieve this. Netscape recognizes the BORDER attribute on FRAMESET. It can be set to 0, in which case the border will not be shown, and the spacing will be set to zero. Microsoft Internet Explorer recognizes the FRAMEBORDER and FRAMESPACING attributes on FRAMESET, but in some versions also on FRAME for individual frames. Both attributes must be set to 0. So, the most widely supported way to display borderless frames is <FRAMESET ... BORDER=0 FRAMEBORDER=0 FRAMESPACING=0>. Note that these attributes are proprietary and not part of the HTML 4.0 specification. Also, removing the border around a frame makes it impossible to resize it, as this border is also used in most GUIs to change the size of the window. 8.9. How do I change the title of a framed document? The title displayed is the title of the frameset document rather than the title s of any of the pages within frames. To change the title displayed, link to a new frameset document using TARGET="_top" (replacing the entire frameset). 8.10. Why aren't my frames the exact size I specified? Netscape Navigator seems to round pixel-based frame dimensions to the nearest whole percentage, and to use those percentage-based dimensions when laying out the frames. Thus, frames with pixel-based dimensions will be rendered with a slightly different size than that specified in the frameset document. There is no way to prevent this behavior, and the rounding error will vary depending on the exact size of the browser window. To accomodate this, you should design your site to adapt to variations in the browser's presentation. This is a good idea in general, but especially so in this situation. 8.11. Are there any problems with using frames? The fundamental problem with the design of frames is that framesets create states in the browser that are not addressable. Once any of the frames within a frameset changes from its default content, there is no longer a way to address the current state of the frameset. It is difficult to bookmark - and impossible to link or index - such a frameset state. It is impossible to reference such a frameset state in other media. When the sub-documents of such a frameset state are accessed directly, they appear without the context of the surrounding frameset. Basic browser functions (e.g., printing, moving forwards/backwards in the browser's history) behave differently with framesets. Furthermore, frames focus on layout rather than on information structure, and many authors of framed sites neglect to provide useful alternative content in the <NOFRAMES> element. Both of these factors cause accessibility problems for browsers that differ significantly from the author's expectations and for searc h engines. For further discussion, see <URL:http://www.htmlhelp.com/design/frames/whatswrong.html> ------------------------------------------------------------ For additions or omissions to this FAQ, please contact <darin@htmlhelp.com>. All information contained herein was originally compiled by members of the Web Design Group, principally Arnoud "Galactus" Engelfriet, John Pozadzides, and Darin McGrew. Additional input has been provided by Boris Ammerlaan, Lori Atwater, Alex Bell, Stan Brown, Roger Carbol, Alex Chapman, Jan Roland Eriksson, Jon Erlandson, Mar k Evans, Alan Flavell, Lucie Gelinas, Bjoern Hoehrmann, Tina Marie Holmboe, Peter Jones, Nick Kew, Jukka Korpela, Simon Lee, Nick Lilavois, Neal McBurnett, Glen McDonald, Dan McGarry, Ken O'Brien, Timothy Prodin, Steve Pugh, Liam Quinn, Colin Reynolds, Kai Sch�tzl, Doug Sheppard, Sue Sims, Toby Speight, Warren Steel, Ian Storms, Peter Thomson, Daniel Tobias, and Diane Wilson. Thanks everyone! ------------------------------------------------------------ Web Design Group Copyright � 1996-1999. All rights reserved.

Path: senator-bedfellow.mit.edu!bloom-beacon.mit.edu!newsswitch.lcs.mit.edu!newsfeed.berkeley.edu!news-feed.ifi.uio.no!ifi.uio.no!not-for-mail From: John Pozadzides Newsgroups: comp.infosystems.www.authoring.html,comp.answers,news.answers Subject: comp.infosystems.www.authoring.html FAQ -- Supersedes: Followup-To: comp.infosystems.www.authoring.html Date: 2 Mar 2000 00:00:12 GMT Organization: Dept. of Informatics, Univ. of Oslo, Norway Lines: 2057 Approved: news-answers-request@MIT.EDU Expires: Thu, 16 Mar 2000 00:00:09 GMT Message-ID: Reply-To: john@htmlhelp.com NNTP-Posting-Host: mimming.ifi.uio.no X-Trace: maud.ifi.uio.no 951955212 26428 129.240.66.180 (2 Mar 2000 00:00:12 GMT) X-Complaints-To: abuse@ifi.uio.no NNTP-Posting-Date: 2 Mar 2000 00:00:12 GMT Xref: senator-bedfellow.mit.edu comp.infosystems.www.authoring.html:272659 comp.answers:39877 news.answers:178352 Maintainer: darin@htmlhelp.com Archive-name: www/authoring-faq Copyright: Copyright.+(1996-98. Web Design Group) Posting-Frequency: Every 14 days The Web Design Group Web Authoring FAQ ------------------------------------------------------------ This list of Frequently Asked Questions is maintained by the WDG and was last updated on November 29, 1999. It may be found at the following URLs: * (index of HTML version) * (single-file HTML version) * (single-file text version) If you would like to contribute to this FAQ, please send mail to . All contributors will be listed at the bottom of the FAQ. Index 1. Getting Started 1. What is everyone using to write HTML? 2. Where can I find a list of all the current HTML tags? 3. How can I show HTML examples without them being interpreted as part of my document? 4. How do I get a so-and-so character in my HTML? 5. Should I put quotes around attribute values? 6. How can I include comments in HTML? 7. How can I check for errors? 8. What is a DOCTYPE? Which one do I use? 2. Web Publishing 1. Where can I put my newly created Web pages? 2. Where can I announce my site? 3. Is there a way to get indexed better by the search engines? 4. How do I prevent my site from being indexed by search engines? 5. How do I redirect someone to my new page? 6. How do I password protect my web site? 7. How do I stop my page from being cached? 8. How do I hide my source? 9. How do I detect what browser is being used? 10. How do I get my visitors' email addresses? 11. Why is my custom 404 message not displayed? 3. Web Design 1. How do I include one file in another? 2. Which should I use, &entityname; or &#number; ? 3. Should I use lower case or upper case for tags? 4. For what screen size should I write? 5. Why does my page display fine in browser X but incorrectly or not at al l in browser Y? 6. Why does the browser show my plain HTML source? 7. How do I freeze the URL displayed in a visitor's browser? 8. How do I make a table which looks good on non-supporting browsers? 9. Can I nest tables within tables? 10. How do I center a table? 11. Can I use percentage values for ? 4. Hyperlinks 1. Should I end my URLs with a slash? 2. How do I link to a location in the middle of an HTML document? 3. How do I link without using the full URL? 4. How do I create a link that opens a new window? 5. How do I create a link that opens a new window of a specific size? 6. How do I get a button which takes me to a new page? 7. How do I get a back button on my page? 8. How do I create a link that sends me email? 9. How do I specify a subject for a mailto: link? 10. How do I link an image to something? 11. How do I eliminate the blue border around linked images? 12. How do I link different parts of an image to different things? 13. How do I turn off underlining on my links? 14. How can I have two sets of links with different colors? 15. How can I make links change when the cursor is over them? 16. Why are my hyperlinks coming out all wrong or not loading? 17. Why does my link work in Internet Explorer but not in Netscape? 5. Other Media 1. How do I let people download a file from my page? 2. Why did my link to a _______ file only download a bunch of characters instead? 3. How do I force a download? 4. How do I make animated GIFs? 5. How can I create a thumbnail image that is linked to the full-sized image? 6. Why am I getting a colored whisker to the left or right of my image? 7. How can I display random images? 8. Why are my images coming out all wrong or not loading? 9. How do I prevent people from saving my images? 10. Can I put markup in ALT text? 11. How do I get an audio file to play automatically when someone visits my site? 12. How can I strip all the HTML from a document to get plain text? 6. Presentational Effects 1. How can I make a custom rule? 2. How can I make a list with custom bullets? 3. Where can I get a "hit counter"? 4. How do I display the current date or time in my document? 5. How do I get scrolling text in the status bar? 6. How do I right align text or images? 7. How can I specify fonts in my Web pages? 8. How do I indent the first line in my paragraphs? 9. How do I indent a lot of text? 10. How do I do a page break? 11. How do I have a fixed background image? 12. How do I have a non-tiled background image? 13. How can I have a custom icon when people bookmark my site? 7. HTML Forms 1. How do I use forms? 2. How do I get form data emailed to me? 3. How do I make a form so it can be submitted by hitting ENTER? 4. How can I make a form with custom buttons? 5. Can I have two or more Submit buttons in the same form? 6. How can I allow file uploads to my web site? 7. How can I use forms for pull-down navigation menus? 8. HTML Frames 1. How do I make a link or form in one frame update another frame? 2. Why do my links open new windows rather than update an existing frame? 3. How do I update two frames at once? 4. How do I get out of a frameset? 5. How do I make sure my framed documents are displayed inside their frameset? 6. Is there a way to prevent getting framed? 7. How do I specify a specific combination of frames instead of the defaul t document? 8. How do I remove the border around frames? 9. How do I change the title of a framed document? 10. Why aren't my frames the exact size I specified? 11. Are there any problems with using frames? 1. Getting Started 1.1. What is everyone using to write HTML? It seems that everyone has a different preference for which tool works best for them. You may find lists of HTML authoring tools at: * http://www.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_We b/HTML_Editors/ * http://www.winfiles.com/ (search "HTML Editors") * http://www.tucows.com/ (Win 95, Win 3.x, Macintosh, OS/2) * http://www.shareware.com/ (search "HTML editor") Keep in mind that typically the less HTML the tool requires you to know, the worse the output of the HTML. In other words, you can always do it better by hand if you take the time to learn a little HTML. 1.2. Where can I find a list of all the current HTML tags? The current W3C Recommendation is HTML 4.0. HTML 4.0 extends HTML 3.2 to includ e support for frames, internationalization, style sheets, advanced tables, and more. HTML 4.0 is not well supported by current browsers, but many of its features can be used safely in non-supporting browsers. Recommended materials on HTML 4.0: * http://www.w3.org/TR/REC-html40/ -- the official HTML 4.0 Recommendation * http://www.htmlhelp.com/reference/html40/ -- a handy reference, with notes on using poorly supported features safely Recommended materials on HTML 3.2: * http://www.w3.org/TR/REC-html32 -- the official HTML 3.2 Recommendation * http://www.htmlhelp.com/reference/wilbur/ -- a more readable version of the above * http://www.hut.fi/~jkorpela/HTML3.2/ -- Jukka Korpela's "Learning HTML 3.2 by Examples" Some materials on browser-specific versions of HTML: * http://www.blooberry.com/html/supportkey/a.htm -- Brian Wilson's checklist of browser support for HTML tags and attributes * http://developer.netscape.com/docs/manuals/htmlguid/index.htm -- a list of all available Netscape HTML tags * http://msdn.microsoft.com/workshop/author/html/reference/elements.asp#ie40_ html -- a list of all available Microsoft HTML tags 1.3. How can I show HTML examples without them being interpreted as part of my document? Within the HTML example, first replace the "&" character with "&" everywher e it occurs. Then replace the "<" character with "<" and the ">" character wit h ">" in the same way. The next Q&A addresses the more general issue of representing arbitrary characters in HTML documents. 1.4. How do I get a so-and-so character in my HTML? The safest way to do HTML is in (7-bit) US-ASCII, and expressing characters fro m the upper half of the 8-bit code by using HTML entities. See the answer to "Which should I use, &entityname; or &#number; ?" Working with 8-bit characters can also be successful in many practical situations: Unix and MS-Windows (using Latin-1), and also Macs (with some reservations). The available characters are those in ISO-8859-1, listed at . On the Web, these are the onl y characters widely supported. In particular, characters 128 through 159 as used in MS-Windows are not part of the ISO-8859-1 code set and will not be displayed as Windows users expect. This includes the em dash, en dash, curly quotes, bullet, and trademark symbol; neither the actual character nor &#nnn; is correct. (See the last paragraph of this answer for more about those characters.) On platforms whose own character code isn't ISO-8859-1, such as MS DOS, Macs, there may be problems: you'd have to use text transfer methods that convert between the platform's own code and ISO-8859-1 (e.g Fetch for the Mac), or convert separately (e.g GNU recode). Using 7-bit ASCII with entities avoids those problems, and this FAQ is too small to cover other possibilities in detail. Mac users - see the notes at the above URL. If you run a web server (httpd) on a platform whose own character code isn't ISO-8859-1, such as a Mac, or IBM mainframe, it's the job of the server to convert text documents into ISO-8859-1 code when sending them to the network. If you want to use characters outside of the ISO-8859-1 repertoire, you must us e HTML 4.0 rather than HTML 3.2. See the HTML 4.0 Recommendation at and the Babel site at for more details. Another useful resource for internationalization issues is at . 1.5. Should I put quotes around attribute values? It depends. It is never wrong to use them, but you don't have to if the attribute value consists only of letters (A-Za-z), digits, periods and hyphens. This is explained in the HTML 2.0 specs. Be careful when your attribute value includes double quotes, for instance when you want ALT text like "the "King of Comedy" takes a bow" for an image. Humans can parse that to know where the quoted material ends, but browsers can't. You have to code the attribute value specially so that the first interior quote doesn't terminate the value prematurely. There are two main techniques: * Escape any quotes inside the value with " so you don't terminate the value prematurely: ALT="the "King of Comedy" takes a bow". (" is not part of the formal HTML 3.2 spec, though most current browsers support it.) * Use single quotes to enclose the attribute value: ALT='the "King of Comedy" takes a bow'. Both these methods are correct according to the spec and are supported by current browsers, but both were poorly supported in some earlier browsers. The only truly safe advice is to rewrite the text so that the attribute value need not contain quotes, or to change the interior double quotes to single quotes, like this: ALT="the 'King of Comedy' takes a bow". Note that XHTML 1.0 (a reformulation of HTML 4.0 as an XML 1.0 application) requires attribute values to be quoted. 1.6. How can I include comments in HTML? A comment declaration starts with "". A comment starts and ends with "--", and does not contain any occurrence of "--" between the beginning and ending pairs. This means that the following are all legal HTML comments: * * * * * But some browsers do not support the full syntax, so we recommend you follow this simple rule to compose valid and accepted comments: An HTML comment begins with "" and does not contain "--" or ">" anywhere in the comment. See for a more complete discussion. 1.7. How can I check for errors? Various software is available to find errors in your web documents automatically. HTML validators are programs that check HTML documents against a formal definition of HTML syntax and then output a list of errors. Validation i s important to give the best chance of correctness on unknown browsers (both existing browsers that you haven't seen and future browsers that haven't been written yet). HTML linters (checkers) are also useful. These programs check documents for specific portability problems, including some caused by invalid markup and others caused by common browser bugs. Linters may pass some invalid documents, and they may fail some valid ones. All validators are functionally equivalent; while they may have different reporting styles, they will find the same errors given identical input. Different linters are programmed to look for different problems, so their reports will vary significantly from each other. Also, some programs that are called validators (e.g. the "CSE HTML Validator") are really linters/checkers. They are still useful, but they should not be confused with real HTML validators. When checking a site for errors for the first time, it is often useful to identify common problems that occur repeatedly in your markup. Fix these problems everywhere they occur (with an automated process if possible), and the n go back to identify and fix the remaining problems. While checking for errors in the HTML, it is also a good idea to check for hypertext links which are no longer valid. There are several link checkers available for various platforms which will follow all links on a site and retur n a list of the ones which are non-functioning. You can find a list of validators, linters, and link checkers at . Especially recommended is the use of an SGML-based validator such as the WDG HTML Validator or W3C HTML Validation Service . 1.8. What is a DOCTYPE? Which one do I use? According to HTML standards, each HTML document begins with a DOCTYPE declaration that specifies which version of HTML the document uses. The DOCTYPE declaration is useful primarily to SGML-based tools like HTML validators, which must know which version of HTML to use in checking the document's syntax. Browsers generally ignore DOCTYPE declarations. See for information on choosing an appropriate DOCTYPE declaration. Note that the public identifier section of the DOCTYPE declaration is case sensitive. Some versions of Netscape Composer are known to insert the lower-cas e "-//w3c//dtd html 4.0 transitional//en", rather than the correct mixed-case "-//W3C//DTD HTML 4.0 Transitional//EN". 2. Web Publishing 2.1. Where can I put my newly created Web pages? Many ISPs offer web space to their dial-up customers. Typically this will be less than 5MB, and there may be other restrictions; for example, many do not allow commercial use of this space. There are several companies and individuals who offer free web space. This usually ranges from 100KB up to 1MB, and again there are often limitations on its use. They may also require a link to their home page from your pages. The following have pointers to providers of free web space: * * There are also many web space providers (aka presence providers) who will sell you space on their servers. Prices will range from as little as $1 per month, u p to $100 per month or more, depending upon your needs. Non-virtual Web space is typically the cheapest, offering a URL like: http://www.some-provider.com/yourname/ For a little more, plus the cost of registering a domain name, you can get virtual web space, which will allow you to have a URL like http://www.yourname.com/. If you have some permanent connection to the Internet, perhaps via leased line from your ISP then you could install an httpd and operate your own Web server. There are several Web servers available for almost all platforms. If you just wish to share information with other local users, or people on a LA N or WAN, you could just place your HTML files on the LAN for everyone to access, or alternatively if your LAN supports TCP/IP then install a Web server on your computer. 2.2. Where can I announce my site? * comp.infosystems.www.announce -- a moderated newsgroup specifically geared toward this subject. You need to obtain its FAQ list before posting to it. * http://www.submit-it.com/ lets you submit site information to 10 different major index sites for free. If you wish to pay you may submit your site to more than 400 sites. * http://ep.com/faq/webannounce.html is the How to Announce your New Web Site FAQ. 2.3. Is there a way to get indexed better by the search engines? There is no single technique, but a number of factors can help. * Search engines index the textual content of your site, so use a meaningful , use meaningful headings (<H1>, <H2>, and so on), and provide meaningful ALT text for images. * Many search engines ignore frames, so avoid them, and be sure to provide useful NOFRAMES content if you do use them. * Most earch engines ignore image maps, forms, and JavaScript, so make sure that navigating your site doesn't depend on them. Provide normal links for site navigation. * Avoid using META refresh, because many search engines penalize sites that use it (META refresh has been used to trick search engines). * The indexing programs of some search engines (including AltaVista and Infoseek) will also take into account <META NAME="keywords" CONTENT="..."> tags that appear in the <HEAD> part of your documents. However, META keywords have been used to trick search engines, so many will ignore your keywords list if you repeat a given keyword too often. At this writing, "to o often" means "more than 7 times" to some popular engines, but that may change in the future as indexing programs are changed to defend against trickery. * If you include a <META NAME="description" CONTENT="..."> tag in the <HEAD> part of your documents, then some search engines will use the content of this tag as your site's description when displaying search results. This won't affect your ranking in searches, but it can help search engine users understand what your site offers when a search does find your site. Note that the CONTENT attribute of the META keywords and description tags may contain up to 1022 characters, but no markup other than entities. You might want to preview your site with a text-only browser like Lynx, to get an idea of how your site appears to search engines. Search Engine Watch at <URL:http://searchenginewatch.com/> is a Web site dedicated to search engines and strategies for Web page authors. 2.4. How do I prevent my site from being indexed by search engines? See <URL:http://info.webcrawler.com/mak/projects/robots/exclusion.html>. 2.5. How do I redirect someone to my new page? The most reliable way is to configure the server to send out a redirection instruction when the old URL is requested. Then the browser will automatically get the new URL. This is the fastest and most efficient way, and is the only wa y described here that can convince indexing robots to phase out the old URL. For configuration details consult your server admin or documentation (with NCSA or Apache servers, use a Redirect statement in .htaccess). If you can't set up a redirect, there are other possibilities. These are inferior because they tell the search engines that there's still a page at the old location, not that the page has moved to a new location. But if it's impossible for you to configure redirection at your server, here are two alternatives: * Put up a small page with text like "This page has moved to http://new.url/ -- please adjust your bookmarks." * A Netscape and MSIE solution, which doesn't work on many other browsers (an d screws up the "back" button in Netscape) is: <META HTTP-EQUIV="Refresh" CONTENT="x; URL=new.URL"> which will load the new URL after x seconds. This should go in the HEAD of the document. But if you do this, also include a short text saying "Documen t moved to new URL so-and-so" for other browsers. (The screwing-up bit refers to the fact that if you press "Back" after you have been redirected, you will be taken to the document with the META refresh. Then the refresh will be activated, and so you'll jump to the page you just tried to leave.) 2.6. How do I password protect my web site? Password protection is done through HTTP authentication. The configuration details vary from server to server, so you should read the authentication section of your server documentation. Contact your server administrator if you need help with this. For example, if your server is Apache, see <URL:http://www.apache.org/docs/misc/FAQ.html#user-authentication>. 2.7. How do I stop my page from being cached? Browsers cache web documents; they store local copies of documents to speed up repeated references to documents that haven't changed. Also, many browsers are configured to use public proxy caches, which serve many users (e.g., all customers of an ISP, or all employees behind a corporate firewall). To effectively control how your documents are cached you must configure your serve r to send appropriate HTTP headers. The configuration details vary from server to server, so check your server documentation. The Expires header is understood by virtually all caches. The cached document will be retrieved again automatically once it has expired. The Expires header must contain an HTTP date, which must be Greenwich Mean Time (GMT), not local time. HTTP 1.1 introduced the Cache-Control header, which provides more flexibility for telling caches how to handle the document. For more information, see the HTTP 1.1 draft (see <http://www.w3.org/Protocols/>). The Pragma header is generally ineffective because its meaning is not standardized and few caches honor it. Using <META HTTP-EQUIV=...> elements in HTML documents is also generally ineffective; some browsers may honor such markup, but other caches ignore it completely. Further discussion can be found at <http://www.mnot.net/cache_docs/>. 2.8. How do I hide my source? You can't. The HTML source is necessary for the browser to display your document; you must send the complete, unencrypted source to the browser. Even i f a particular browser doesn't have a "View Source" feature, there are many that do, and someone can always retrieve the document by hand (using telnet) or from the browser's cache. There are tricks that make it more difficult for some readers to view or save your source (e.g., tricking newbies into thinking there's nothing there by adding dozens of blank lines to the beginning of the document). However, just a s with tricks that try to protect images from being saved, these tricks have very limited effectiveness and can cause various problems for law-abiding users. 2.9. How do I detect what browser is being used? Many browsers identify themselves when they request a document. A CGI script will have this information available in the HTTP_USER_AGENT environment variable, and it can use that to send out a version of the document which is optimized for that browser. Keep in mind not all browsers identify themselves correctly. Microsoft Internet Explorer, for example, claims to be "Mozilla" to get at Netscape enhanced documents. And of course, if a cache proxy keeps the Netscape enhanced document, someone with another browser will also get this document if he goes through the cache. For these reasons and others, it is not a good idea to play the browser guessin g game. 2.10. How do I get my visitors' email addresses? You can't. Although each request for a document is usually logged with the name or address of the remote host, the actual username is almost never logged as well. This is mostly because of performance reasons, as it would require that the server uses the ident protocol to see who is on the other end. This takes time. And if a cache proxy is doing the request, you don't get anything sensible. But just stop to think for a minute... would you really want every single site you visit to know your email address? Imagine the loads of automated thank you' s you would be receiving. If you visited 20 sites, you would get at least 20 emails that day, plus no doubt they would send you invitations to return later. It would be a nightmare as well as an invasion of privacy! In Netscape 2.0, it was possible to automatically submit a form with a mailto a s action, using JavaScript. This would send email to the document's owner, with the address the visitor configured in the From line. Of course, that can be "mickey.mouse@disney.com". This was fixed by Netscape 2.01. The most reliable way is to put up a form, asking the visitor to fill in his email address. To increase the chances that visitors will actually do it, offer them something useful in return. 2.11. Why is my custom 404 message not displayed? Recent versions of Internet Explorer default to "friendly" HTTP error messages. When a special HTTP response (e.g., a 404 response) is shorter than 512 bytes, the browser substitutes its own message for the one delivered by the server. As a user of Internet Explorer, you can disable this feature in the "Advanced" options panel. As a web author, your only recourse is to make the error page larger. 3. Web Design 3.1. How do I include one file in another? HTML itself offers no way to seamlessly incorporate the content of one file int o another. True dynamic inclusion of one HTML document (even in a different "charset") int o another is offered by the OBJECT element, but due to shortcomings of browser versions in current use, it seems unwise to rely on this yet for essential content. The same can be said for IFRAME. Two popular ways of including the contents of one file seamlessly into another for the WWW are preprocessing and server-side inclusion. Preprocessing techniques include the C preprocessor and other generic text manipulation methods, and several HTML-specific processors. But beware of makin g your "source code" non-portable. The HTML can only be validated after pre-processing, so the typical cycle "Edit , Check, Upload" becomes "Edit, Preprocess, Check, Upload" (here, "Check" include s whatever steps you use to preview your pages: validation, linting, management walk-through etc.; and "upload" means whatever you do to finally publish your new pages to the web server). A much more powerful and versatile pre-processing technique is to use an SGML processor (such as the SP package) to generate your HTML; this can be self-validating. Examples of server-side inclusion are Server Side Includes "SSI" (Apache, NCSA and some other web servers) and "ASP"; processing occurs at the time the documents are actually retrieved. A typical inclusion looks like  but be sure to consult your own server's documentation, as the details vary somewhat between implementations. The whole directive gets replaced by the contents of the specified file. Using server-side inclusion (a potentially powerful tool) merely as a way to insert static files such as standard header/footers has implications for perceived access speed and for server load, and is better avoided on heavily loaded servers. If you use it in this way, consider making the result cacheable (e.g., via "XBitHack full" on Apache; setting properties of the "Response" object in ASP). Details are beyond the scope of this FAQ but you may find this useful: http://www.pobox.com/~mnot/cache_docs/ Proper HTML validation of server-side inclusion is only possible after server-side processing is done, e.g. by using an on-line validator that retrieves the document from the server. 3.2. Which should I use, &entityname; or &#number; ? In HTML, characters can be represented in three ways: 1. a properly coded character, in the encoding specified by the "charset" attribute of the "Content-type:" header; 2. a character entity (&entityname;), from the appropriate HTML specification (HTML 2.0/3.2, HTML 4.0 etc.); 3. a numeric character reference (&#number;) that specifies the Unicode reference of the desired character. We recommend using decimal references; hexadecimal references are less widely supported. In theory these representations are equally valid. In practice, authoring convenience and limited support by browsers complicate the issue. HTTP being a guaranteed "8-bit clean" protocol, you can safely send out 8-bit o r multibyte coded characters, in the various codings that are supported by browsers. A. HTML 2.0/3.2 (Latin-1) By now there seems no convincing reason to choose &entityname; versus &#number; , so use whichever is convenient. If you can confidently handle 8-bit-coded characters this is fine too, probably preferred for writing heavily-accented languages. Take care if authoring on non-ISO-8859-based platforms such as Mac, Psion, IBM mainframes etc., that your upload technique delivers a correctly coded document to the server. Using &-representations avoids such problems. B. A single repertoire other than Latin-1 In such codings as ISO-8859-7 Greek, koi8-r Russian Cyrillic, and Chinese, Japanese and Korean (CJK) codings, use of coded characters is the most widely supported and used technique. Although not covered by HTML 3.2, browsers have supported this quite widely for some time now; it is a valid option within the HTML 4.0 specification--use a validator such as the WDG HTML Validator at http://www.htmlhelp.com/tools/validator/ which supports HTML 4.0 and understand s different character encodings. Browser support for coded characters may depend on configuration and font resources. In some cases, additional programs called "helpers" or "add-ins" supply virtual fonts to browsers. "Add-in" programs have in the past been used to support numeric references to 15-bit or 16-bit code protocols such as Chinese Big5 or Chinese GB2312. In theory you should be able to include not only coded characters but also Unicode numeric character references, but browser support is generally poor. Numeric references to the "charset-specified" encoding may appear to produce th e desired characters on some browsers, but this is wrong behavior and should not be used. Character entities are also problematical, aside from the HTML-significant characters <, & etc. C. Internationalization per HTML 4.0 Recent versions of the popular browsers have support for some of these features , but at time of writing it seems unwise to rely on this when authoring for a general audience. If you'd like to explore the options, you can find comprehensive background documentation and some practical suggestions at * http://www.czyborra.com/ * http://www.hut.fi/u/jkorpela/chars.html * http://ppewww.ph.gla.ac.uk/~flavell/charset/ 3.3. Should I use lower case or upper case for tags? Tags are case insensitive, so it doesn't matter. This is just a matter of style . (You may have noticed that this FAQ is not absolutely consistent in capitalization.) Many people prefer upper case, as it makes the tags "stand out " better amongst the text. Attribute names can also be upper or lower case, as you prefer. But some attribute values are case sensitive. For example, <OL TYPE=A> and <OL type=A> are the same, but <OL TYPE=a> is different from both of them. (For clearer communication, it's worth getting the terminology right. In this example, OL is the element, TYPE is the attribute name, and A and a are the attribute values. The tag is <OL TYPE=A>.) Entity names like are sometimes incorrectly referred to as tags. They ar e all case sensitive. For example, É and é are two different an d valid entities; &NBSP; is invalid. Note that XHTML 1.0 (a reformulation of HTML 4.0 as an XML 1.0 application) requires element and attribute names to be in lower case. 3.4. For what screen size should I write? HTML does not depend on screen size. Normally, the text will be wrapped by the browser when the end of its display area is encountered. (Note that graphical browsers are often used with windows that are smaller than the full area of the screen.) Preformatted lines (text within <PRE> elements) should only ever exceed 70 characters if the nature of the content makes it unavoidable. Longer lines will cause ugly line breaks on text-mode browsers, and will force horizontal scrolling on graphical browsers. Readers strongly dislike horizontal scrolling, except where they can realise that the nature of the content made it inevitable . Images cannot be wrapped, so you have to be careful with them. It seems that 40 0 or 500 pixels is a reasonable width; anything above 600 will mean a certain percentage of users will have to scroll to see the rightmost bit. This percentage increases with your image width. Keep in mind that not everyone runs his browser at full screen! (WebTV users have no ability to scroll horizontally, so anything beyond 544 pixels will be compressed by their browser. Some other devices may be even more limited.) 3.5. Why does my page display fine in browser X but incorrectly or not at all i n browser Y? There are several possibilities. First, you may have some incorrect HTML. Browsers vary in their ability to gues s what you meant. For instance, Netscape is much more fussy about tables than MS Internet Explorer, so a page with incorrect tables may look fine in MSIE but no t display at all in Netscape. See the answer to "How can I check for errors?" for tips on finding your HTML errors. (In fact, even correct nested tables may not display correctly in Netscape. See "Can I nest tables within tables?" below for what you can do about that.) Second, you may have valid HTML that different browsers interpret differently. For instance, it is not clear from the spec what should be done with a string o f characters. Some browsers will collapse them for rendering as a single space; others will render one space per . Third, your server may be sending incorrect MIME types for some of your files. Internet Explorer incorrectly ignores server-provided MIME types, so it sometimes "does the right thing" when the server is misconfigured. Other browsers correctly heed the server-provided MIME types, so they will reveal server misconfigurations. Other possibilities are a bug in one or the other browser, or different user option settings. See also the answers to "Why are my hyperlinks coming out all wrong or not loading?" and "Why are my images coming out all wrong or not loading?" 3.6. Why does the browser show my plain HTML source? If Microsoft Internet Explorer displays your document normally, but other browsers display your plain HTML source, then most likely your web server is sending the document with the MIME type "text/plain". Your web server needs to be configured to send that filename with the MIME type "text/html". See the answer to "Why did my link to a _______ file only download a bunch of character s instead?" for more details. 3.7. How do I freeze the URL displayed in a visitor's browser? This is a "feature" of using frames: The browser displays the URL of the frameset document, rather than that of the framed documents. (See the answer to the question "How do I specify a specific combination of frames instead of the default document?"). However, this behavior can be circumvented easily by the user. Many browsers allow the user to open links in their own windows, to bookmark the document in a specific frame (rather than the frameset document), or to bookmark links. Thus, there is no reliable way to stop a user from getting the URL of a specific document. Furthermore, preventing users from bookmarking specific documents can only antagonize them. A bookmark or link that doesn't find the desired document is useless, and probably will be ignored or deleted. 3.8. How do I make a table which looks good on non-supporting browsers? See Alan Flavell's document on tables for a good discussion at <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/www/tablejob.html>. 3.9. Can I nest tables within tables? Yes, a table can be embedded inside a cell in another table. Here's a simple example: <table> <tr> <td>this is the first cell of the outer table</td> <td>this is the second cell of the outer table, with the inner table embedded in it<br> <table> <tr> <td>this is the first cell of the inner table</td> <td>this is the second cell of the inner table</td> </tr> </table> </td> </tr> </table> The main caveat about nested tables is that Netscape has problems with them if you don't close your TD and TR tags meticulously. You're best advised to includ e every </TD> and </TR>, even though the HTML spec doesn't require them; otherwis e Netscape users may not be able to view your page. 3.10. How do I center a table? The "correct" way of doing it is <TABLE ALIGN=CENTER>, but this doesn't work in several popular browsers. Put <CENTER>; around the entire table for these browsers. This causes some problems with browsers that do support CENTER but not tables, such as Lynx. In these browsers, the contents of the cells are now displayed centered, which is not what is intended. To avoid this, you can put the cell's contents in <P ALIGN=left> or <DIV ALIGN=left> depending on the amount of text in the cell. 3.11. Can I use percentage values for <TD WIDTH=...>? The HTML 3.2 and HTML 4.0 specifications allow only integer values (representin g a number of pixels) for the WIDTH attribute of the TD element. However, the HTM L 4.0 DTD allows percentage (and other non-integer) values, so an HTML validator will not complain about <TD WIDTH="xx%">. It should be noted that Netscape and Microsoft's browsers interpret percentage values for <TD WIDTH=...> differently. However, their interpretations (and thos e of other table-aware browsers) happen to match when combined with <TABLE WIDTH="100%">. In such situations, percentage values can be used relatively safely, even though they are prohibited by the public specifications. 4. Hyperlinks 4.1. Should I end my URLs with a slash? The trailing slash is used to distinguish between directory and file URLs. A file URL is an URL for a file, and a directory URL refers to a directory. For example, the URL for the WDG's HTML reference is http://www.htmlhelp.com/reference/ and the URL for the overview of HTML 3.2 elements is http://www.htmlhelp.com/reference/wilbur/overview.html If you request a directory URL without the trailing slash, the browser will actually ask for a FILE with that name. This file doesn't exist on the server, so the server sends back a message saying that the browser should ask for the directory. It uses a redirection message for this. The browser then sends another request, this time for the directory, and finally gets what was asked for in the first place. This wastes time and network resources. When you write a document, all directory URLs should end with a slash. Since yo u already know you are linking to a directory, why force the user to make that second request, when it could have been done using only one? And by the way, it is NOT the browser which appends the slash. The browser cannot know if what you are asking for is a file or directory, not even when th e final part of the URL does not have an extension. http://www.somewhere.com/src/something/README is a perfectly valid URL, has no extension in the final part, yet refers to a file and not a directory. The only apparent exception is when you refer to an URL with just a hostname. Since it is obvious that when you use http://www.htmlhelp.com you actually want the main index "/" from our server, you do not have to include the / in this case. It is regarded as good style to do so, however. For a full discussion of the proper form of URLs, see RFC 1738 at <URL:http://www.cis.ohio-state.edu/htbin/rfc/rfc1738.html> and, for relative URLs, RFC 1808 at <URL:http://www.cis.ohio-state.edu/htbin/rfc/rfc1808.html>. 4.2. How do I link to a location in the middle of an HTML document? First, identify the destination of the link with a named anchor (an anchor that uses the NAME attribute). For example: <H2><A NAME="section2">Section 2: Beyond Introductions</A></H2> Second, link to the named anchor. The URL of the named anchor is the URL of the document, with "#" and the name of the anchor appended. For example, elsewhere in the same document you could use: <A HREF="#section2">go to Section 2</A> Similarly, in another document you could use: <A HREF="thesis.html#section2">go to Section 2 of my thesis</A> 4.3. How do I link without using the full URL? Links that do not specify the full URL are called relative links. Before the browser can request the linked document, it must generate the full URL using th e relative URL and the URL of the current document. First, the browser strips everything after the last slash ("/") in the URL of the current document. Second, it moves up one level in the URL hierarchy for each "../" at the beginning of the relative URL, removing the leading "../" strings from the relative URL as it does so. Third, it appends the relative URL to get the final URL. Some examples may help make this clear. Assuming that the current document is <URL:http://www.htmlhelp.com/faq/html/links.html>: "all.html" refers to <URL:http://www.htmlhelp.com/faq/html/all.html> "../" refers to <URL:http://www.htmlhelp.com/faq/> "../cgifaq.html" refers to <URL:http://www.htmlhelp.com/faq/cgifaq.html> "../../reference/" refers to <URL:http://www.htmlhelp.com/reference/> For more details on using and resolving relative URLs, see "Using Relative URLs " <URL:http://www.stack.nl/%7Egalactus/html/urls.html. 4.4. How do I create a link that opens a new window? <A TARGET="_blank" HREF=...> opens a new, unnamed window. <A TARGET="foobar" HREF=...> opens a new window named "foobar", provided that a window or frame by that name does not already exist. Note that links that open new windows can be annoying to your readers if there is not a good reason (from the reader's perspective) for them. 4.5. How do I create a link that opens a new window of a specific size? With HTML, there is no way to control the size (or window decoration, or other features) of a new window. However, in JavaScript you can specify such details when using the window.open() function. Start with a normal HTML link (possibly one that opens in a new window as described in the answer to the previous question). Then use the ONCLICK attribute to open a window with the desired appearance for those readers with JavaScript supported and enabled. The following example specifies a window name d "popup" that is 300 pixels by 150 pixels. <A HREF="foo.html" TARGET="popup" ONCLICK="window.open('foo.html', 'popup', 'width=300,height=150'); return false">View Foo</A> Used in this manner, JavaScript can specify a new window with the desired appearance, without blocking access when JavaScript is unsupported/disabled. 4.6. How do I get a button which takes me to a new page? This is best done with a small form: <FORM ACTION="http://url.you.want.to.go.to/" METHOD=GET> <INPUT TYPE=submit VALUE="Text on button" NAME=foo> </FORM> If you want to line up buttons next to each other, you will have to put them in a one-row table, with each button in a separate cell. Note that search engines might not find the target document unless there is a normal link somewhere else on the page. A go-to-other-page button can also be coded in JavaScript, but the above is standard HTML and works for more readers. 4.7. How do I get a back button on my page? In HTML, this is impossible. Going "back" means that you go to the previous pag e in your history. You might be able to create a link to the URL specified in the "HTTP_REFERER" environment variable in your document, but that only creates a link to a new location in your history. Even worse, the information in that variable can be plain wrong. Some browsers incorrectly send the variable when you use a bookmark or type in an URL manually, and some don't send that variabl e at all. This would result in an empty link. A JavaScript could use "history.back()" to do this, but this only works in Netscape 2 or higher and MSIE 3 or higher, and even then only if the user has not disabled JavaScript. For a more detailed explanation, please see Abigail's "Simulating the back button" at <URL:http://www.foad.org/%7Eabigail/HTML/Misc/back_button.html>. 4.8. How do I create a link that sends me email? Use a mailto: link, for example Send me email at <A HREF="mailto:me@mydomain.com">me@mydomain.com</A>. 4.9. How do I specify a subject for a mailto: link? You can't, not in any reliable way. The methods that are frequently posted don' t do the job on all browsers (or even all popular browsers), and many of them hav e an important drawback: if your visitors are using an older browser such as Netscape 1.22, their mail will be lost. If you really need a subject, you can do it by providing a form on your page, which submits data to a CGI program that emails the form data to you with your desired subject line. However, the form must have an input field for the visitor's email address, and you must hope that the visitor enters it correctly . Here are some other ways to transmit subject-type information: * Create email aliases that are used only for certain mailto links, so you'll know that anything sent to a given alias is in response to the correspondin g Web page(s). * The mail handlers for many Web browsers include an "X-Url" header that specifies the URL of the Web page that contained the mailto link. If you configure your mail reader to display this header, you'll see which Web pag e the sender is responding to much of the time. * Use <A HREF="mailto:user@site" TITLE="Your Subject">. Most browsers will ignore the TITLE attribute, but some minor browsers will use it as a subjec t for the email message. All browsers will send the mail. * Use <A HREF="mailto:user@site?subject=Your%20Subject">, which puts "Your Subject" (the space is encoded as "%20") in the "Subject" header field of the email message in most current browsers. The details of this recent RFC can be found at <URL:http://info.internet.isi.edu/in-notes/rfc/files/rfc2368.txt>. Note however that you will lose mail from users of older browsers, so you should consider whether the pre-filled subject is worth lost mail. 4.10. How do I link an image to something? Just use the image as the link content, like this: <A HREF=...><IMG ...></A> 4.11. How do I eliminate the blue border around linked images? Use the BORDER="0" attribute in the <IMG> element. For example: <A HREF="doc.html"><IMG SRC="doc.gif" ALT="View document." BORDER="0"></A> 4.12. How do I link different parts of an image to different things? Use an image map. Client-side image maps don't require server-side processing, so response time is faster. Server-side image maps hide the link definitions from the browser, and can act as a backup for client-side image maps for the fe w very old browsers that support server-side image maps but not client-side image maps. The configuration details of server-side image maps vary from server to server. Refer to your server documentation for details. Client-side image maps are implemented with HTML. The MAP element defines an individual image map and the AREA element defines specific linked areas within that image map. The USEMAP attribute of the IMG element associates an image map with a specific image. A detailed explanation (with examples) is available at <http://www.htmlhelp.com/reference/html40/special/map.html>. A tutorial is available at <http://ppewww.ph.gla.ac.uk/~flavell/www/imgmaptut.html>. 4.13. How do I turn off underlining on my links? If you want to turn off link underlining when you're looking at pages in your browser, check your browser's configuration options. In Netscape 3, for example , see Options | General Preferences | Appearance; in Netscape 4 it's Edit | Preferences | Appearance | Colors; in Internet Explorer see View | Options | General. If you want to prevent links on your page being underlined when your visitors see them, there's no way in HTML to accomplish this. You can suggest this presentation using style sheets by defining a:link, a:visited, a:active {text-decoration: none} 4.14. How can I have two sets of links with different colors? You can suggest this presentation using style sheets. In your style sheet, define something like this: a:link {color: blue; background: white} a:visited {color: purple; background: white} a:active {color: red; background: white} a.foo:link {color: yellow; background: black} a.foo:visited {color: white; background: black} a.foo:active {color: red; background: black} Then use CLASS="foo" to identify the links of the second color in your HTML, like this: <A CLASS="foo" HREF=...>...</A> 4.15. How can I make links change when the cursor is over them? In your style sheet, use the hover pseudo-class to specify a different appearance for links when the cursor is over them. Specify the hover pseudo-class after the link and visited pseudo-classes. For example: A:link { color: blue ; background: white } A:visited { color: purple ; background: white } A:hover { color: red ; background: white } 4.16. Why are my hyperlinks coming out all wrong or not loading? Most likely you forgot to close a quote at the end of the HREF attribute. Alternatively, perhaps you used a ">" character somewhere else inside a tag. Although this is legal, several older browsers will think the tag ends there, s o the rest is displayed as normal text. This especially happens if you use comment tags to "comment out" text with HTML tags. (See the answer to "How can I include comments in HTML?") Although the correct syntax is  (without "--" occurring anywhere inside the comment) , some browsers will think the comment ends at the first ">" they see. Validators will show you any syntax errors in your markup, but checkers such as Weblint and HTMLchek can show you where you are liable to provoke known browser bugs. See also the answer to "How can I check for errors?" 4.17. Why does my link work in Internet Explorer but not in Netscape? Is there a space, #, ?, or other special character in the path or filename? Spaces are not legal in URLs. If you encode the space by replacing it with %20, your link will work. You can encode any character in a URL as % plus the two-digit hex value of the character. (Hex digits A-F can be in upper or lower case.) According to the spec, only alphanumerics and the special characters $-_.,+!*'() need not be encoded. You should encode all other characters when they occur in a URL, except when they're used for their reserved purposes. For example, if you wanted to pass th e value "Jack&Jill" to a CGI script, you would need to encode the "&" character a s "%26", which might give you a URL like the following: http://www.foo.com/foo.cgi?rhyme=Jack%26Jill&audience=child. Note that the "?" and other "&" character in this URL are not encoded since they're used for thei r reserved purposes. See section 2.2 of RFC 1738 at <URL:http://www.w3.org/Addressing/rfc1738.txt> for the full story. 5. Other Media 5.1. How do I let people download a file from my page? Once the file is uploaded to the server, you need only use an anchor reference tag to link to it. An example would be: <a href="../files/foo.zip">Download Foo Now! (100kb ZIP)</a> It is possible that the server might need to be configured for some different file types. (See the next Q&A.) 5.2. Why did my link to a _______ file only download a bunch of characters instead? If you are trying to link to a particular type of file and it is not returning your desired response, chances are that the server needs to have the type configured. Talk to your system administrator about getting them to add the content type. Here is a list of common types that often need configuring: Content Type Description Application/msword Microsoft Word Document application/octet-stream Unclassified binary data (often used for compressed file or executable) application/pdf PDF Document application/wordperfect6.0 WordPerfect 6.0 Document application/zip ZIP archive audio/x-wav WAV audio format audio/midi MIDI audio format audio/x-pn-realaudio RealAudio image/gif GIF image format image/jpeg JPEG image format image/png PNG image format text/html HTML document text/plain Plain text video/mpeg MPEG video format video/quicktime QuickTime video format video/x-msvideo AVI video format Another method of ensuring that your file is properly sent to the client is to compress it into a standard compression format. Virtually all servers are set t o handle the .zip extension and it is widely recognized by users. Some servers (NCSA, Apache, and others) can be configured to support user-configured content types. Details are server dependent, so consult your server admin or documentation. Note that Internet Explorer incorrectly ignores server-provided MIME types, so it sometimes "does the right thing" when the server is misconfigured. Other browsers correctly heed the server-provided MIME types, so they will reveal server misconfigurations. 5.3. How do I force a download? You can't, because the Web doesn't work that way. Here's the explanation. When someone downloads a document, the server tells the browser what type of file it is. The browser then displays it or picks the appropriate helper application. If the server doesn't know the file type, it tells the browser that the file is "text/plain", or just plain text (true for most servers). You may need to ask your server admin to configure this particular file with the MIME type you want. "Forcing" a download is not what you are supposed to do. After all, what is mor e convenient than having the proper application started when I download a particular file? Browsing through a download directory can be quite a pain. And most browsers allow the user to download to disk if they want to. If the file must be saved to disk, if there is absolutely NO other way to handl e it, the MIME type should be "application/octet-stream". 5.4. How do I make animated GIFs? Check out the following resources: * http://members.aol.com/royalef/gifanim.htm * http://www.adobe.com/studio/tipstechniques/GIFanimation/main.html * http://www.webreference.com/dev/gifanim/ 5.5. How can I create a thumbnail image that is linked to the full-sized image? A thumbnail image is just a copy of the full-sized image that has been modified to reduce the size of the file. It is linked to the full-sized image with a normal link: <A HREF="full-sized.jpg"><IMG SRC="thumbnail.jpg" ALT=...></A> There are several techniques for reducing the size of the file for the thumbnai l image, including * resampling/resizing the image to create a physically smaller image; * cropping the image to remove less significant parts of the image; * reducing the image quality to increase compression ratios; and * reducing the size of the color palette (e.g., converting to greyscale). Thumbnail images can use multiple techniques simultaneously. For example, Jakob Nielsen advocates "Relevance-Enhanced Image Reduction", which combines resampling/resizing and cropping. 5.6. Why am I getting a colored whisker to the left or right of my image? This is the result of including "white space" (spaces and newlines) before or after an IMG inside an anchor. For example: <A HREF=...> <IMG SRC=...> </A> will have white space to the left and right of the image. Since many browsers display anchors with colored underscores by default, they will show the spaces to the left and right of the image with colored underscores. Solution: don't leave any white space between the anchor tags and the IMG tag. If the line gets too long, break it inside the tag rather than outside it, like this: <A HREF=...><IMG SRC=...></A> Style checkers such as Weblint will call attention to this problem in your HTML source. 5.7. How can I display random images? There are two basic approaches. The most cache-friendly method is to use a normal IMG tag that refers to a CGI script that randomly redirects the browser to one of several images. There is an example of such a CGI script at <URL:http://www.foad.org/%7Eabigail/CGI/random_images.html>. See the CGI Programming FAQ <URL:http://www.htmlhelp.com/faq/cgifaq.html> for more information about CGI. The second method is to generate the HTML dynamically using a mechanism like Server Side Includes (SSI) or CGI. This method is less cache-friendly, but it does allow the surrounding markup (e.g., HEIGHT and WIDTH attributes, or the URLs for linked/image-mapped images) to vary with the image. If your server supports SSI, the details can be found in your server documentation. 5.8. Why are my images coming out all wrong or not loading? Most likely you forgot to close a quote at the end of the SRC attribute. Alternatively, perhaps you used a ">" character in an ALT text or somewhere els e inside a tag. Although this is legal, several older browsers will think the tag ends there, so the rest is displayed as normal text. This especially happens if you use comment tags to "comment out" text with HTML tags. (See the answer to "How can I include comments in HTML?") Although the correct syntax is  (without "--" occurring anywhere inside the comment) , some browsers will think the comment ends at the first ">" they see. Validators will show you any syntax errors in your markup, but checkers such as Weblint and HTMLchek can show you where you are liable to provoke known browser bugs. See also the answer to "How can I check for errors?" 5.9. How do I prevent people from saving my images? You can't. The image file is necessary for the browser to display your document ; you must send it to the browser. Even if a particular browser doesn't have a "Save Image" feature, there are many that do, and someone can always retrieve the image file by hand (using telnet) or from the browser's cache. There are tricks that make it more difficult for some readers to save your images. However, just as with tricks that try to hide HTML source, these tricks cause various problems for law-abiding users and can't really prevent thieves from saving your images. 5.10. Can I put markup in ALT text? No. Character entities (©, &#nnn; and such) are permitted, though. If you want to know how to write good ALT texts without markup, please see Alan Flavell's essay on choosing ALT texts at <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/alt/alt-text.html>. 5.11. How do I get an audio file to play automatically when someone visits my site? Most browsers support the EMBED element for this, provided that the user has a suitable plug-in for the sound file. You can reach a slightly wider audience if you use BGSOUND as well. To avoid problems with browsers that support both, place the BGSOUND in a NOEMBED container: <EMBED SRC="your_sound_file" HIDDEN=true AUTOSTART=true> <NOEMBED><BGSOUND SRC="your_sound_file"></NOEMBED> For more on the EMBED element, see <URL:http://developer.netscape.com/docs/manuals/htmlguid/tags14.htm#1286379>. See <URL:http://msdn.microsoft.com/developer/sdk/inetsdk/help/dhtml/references/html /BGSOUND.htm> for more information on BGSOUND. Note that these elements are proprietary and not in any HTML standard. (The HTML standard way of doing this is not well supported.) Be aware that some users find it annoying for music to automatically start playing. They may not have the volume set properly on their speakers, or they may be listening to something else. As a courtesy to your users, you may prefer to offer the sound file as a link: <A HREF="your_sound_file">Listen to my sound! (5 kB MIDI)</A> 5.12. How can I strip all the HTML from a document to get plain text? Many browsers have a "Save As..." function that allows you to specify plain tex t as the output format. Another approach is to select all the text, copy it to th e clipboard, and paste it into an editor. Lynx users can use "lynx -dump http://..." on the command line to print to file and append a list of referenced URLs as footnotes. If you want the output file without the footnotes, use the "p" command to "print" to a text file. Some HTML authoring tools have an option to strip all HTML as well. Two program s of note are * HomeSite, available from <URL:http://www.allaire.com/> * DiDa, available from <URL:http://www.faico.net/> If you are looking for another method (in other words you want to make things more difficult on yourself), you can obtain programs which will strip away all HTML markup from a document. Try doing a search at <URL:http://www.altavista.com/> for the phrase "HTML stripper". 6. Presentational Effects 6.1. How can I make a custom rule? Your best option is likely a centered IMG with a line of "--" characters as ALT text: <P ALIGN=center><IMG SRC="custom-line.gif" ALT="--------------------"></P> For an experimental but somewhat more graceful approach, read about CSS1 and th e Decorative HR at <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/www/hrstyle.html>. 6.2. How can I make a list with custom bullets? There are several methods, none completely satisfactory: * Use the list-style property of Cascading Style Sheets. This should be the preferred method of using custom bullets, but unfortunately it's not widely supported by browsers. However, non-supporting browsers will see a normal bullet, so using this method today is not a problem. See <URL:http://www.htmlhelp.com/reference/css/> for more information on style sheets. * Use a <DL> with <DD> tags with preceding images (with ALIGN and suitable AL T text) and no <DT>; this won't be as beautiful as a "real" list. * Use a two-column table, with the bullets in the left column and the text in the right. Since browsers show nothing before downloading the entire table, this can be slow with long lists. * Create the bullet with the indent built in. For example, if you use a bulle t that is 10 pixels across you can make the background 25 pixels (transparent ) and put the bullet all the way on the right. This will create a 15-pixel indent to the left of the bullet. It will add slightly to the byte size of the graphic but since it is all one color it won't add much. This method doesn't work well with any list items that are longer than a line (and remember that you don't know how long a line will be on the visitor's screen). 6.3. Where can I get a "hit counter"? A hit counter is a small script or program that increases a number every time a document is accessed from the server. Why do you want one? If you believe that it will tell you how many times your documents have been accessed, you are mistaken. No counter can keep track of accesses from browser caches or proxy caches. Some counters depend on image-loading to increment; such counters ignore accesses from text-mode browsers, or browsers with image-loading off, or from users who interrupted the transfer. Some counters even require access to a remote site, which may be down or overloaded, causing a delay in displaying your documents. Most web servers log accesses to documents stored on the server machine. These logs may be processed to gain information about the *relative* number of accesses over an extended period. There is no reason to display this number to your viewers, since they have no reference point to relate this number to. Not all service providers allow access to server logs, but many have scripts that will output information about accesses to a given user's documents. Consult you r sysadmin or service provider for details. Counter services and information are available from Yahoo's list of counters: http://www.yahoo.com/Computers/World_Wide_Web/Programming/Access_Counts/ Log analysis tools and scripts are at http://www.yahoo.com/Business_and_Economy/Companies/Computers/Software/Internet /World_Wide_Web/Log_Analysis_Tools/ <URL:http://www.markwelch.com/bannerad/baf_counter.htm> is another good source for counter information. A discussion of the limitations of web-traffic statistics is at <URL:http://www.cranfield.ac.uk/docs/stats/> 6.4. How do I display the current date or time in my document? With server-side includes. Ask your webmaster if this is supported, and what th e exact syntax is for your server. But this will display the local time on the server, not for the client. And if the document is cached, the date will of course be incorrect after some time. JavaScript can be used to display the loca l time for the client, but again, as most people already have one or more clocks on their screen, why display another one? If you plan on putting the current date or time on your pages, using a CGI, JavaScript or VBScript, take an extra breath and consider that it will take resources, add time to the loading of the page, and prevent good caching. If yo u find that you really have a need to use it, for instance to inform readers of the up-times of an FTP server, then by all means do so. If, on the other hand, your only reason is 'it looks cool!' - then reconsider. 6.5. How do I get scrolling text in the status bar? This is not an HTML question; it's done with JavaScript. Check any page which has this feature, and copy the script from the source. This script has two big problems. One, usually it uses the decrement operator (c--) at some point. The "--" sequence in a comment actually closes it on some browsers, so your code may "leak" on those browsers. The same goes for ">". Second, keep in mind that many people consider this even worse than <BLINK>, an d that it also suppresses the status information which normally appears there. It prevents people from knowing where a link goes to. 6.6. How do I right align text or images? You can use the ALIGN=right attribute on paragraphs, divisions, and headers, just as you use ALIGN=center to create centered paragraphs and such. This will right align your text (ragged left). Perhaps what you really want is justified text, in which the left and right edges are both aligned so that all lines are the same length. (This is sometime s incorrectly called "right justify".) There's no way to justify text in HTML 3.2 , but it can be done in a CSS1 style sheet with "text-align: justify". (Before yo u do that, a caveat: though justified text may look pretty, human factors analysi s shows that ragged right is actually easier to read and understand.) For images, you can use <IMG ALIGN=right SRC="..." ALT="..."> before the runnin g text. The image will float at the right margin, and the running text will flow around it. Remember to use <BR CLEAR=right> or <BR CLEAR=all> to mark the end o f the text that is to be affected in this way. 6.7. How can I specify fonts in my Web pages? If you want others to view your web page with a specific font, the most appropriate way is to suggest the font rendering with a style sheet. See: http://www.htmlhelp.com/reference/css/font/font-family.html The FONT element can also be used to suggest a specific font. Use of the FONT element brings numerous usability and accessibility problems, see: http://www.mcsr.olemiss.edu/%7Emudws/font.html More information about the FONT element can be found at: http://www.htmlhelp.com/reference/html40/special/font.html Either way, authors run the risk that a reader's system has a font by the same name but which is significantly different. (e.g., "Chicago" can be a nice text font, or a display font with letters formed by "bullet holes", or a dingbat fon t with building images for creating skylines). Also, authors are limited to choosing a font (or a group of similar fonts) that are commonly available on many systems. If a reader does not have the font installed on their system, they will see a default font. Some browsers may use a less legible substitute font than their normal default font in cases where "the specified font wasn't found". 6.8. How do I indent the first line in my paragraphs? Use a style sheet with the following ruleset: P { text-indent: 5% } See <URL:http://www.htmlhelp.com/reference/css/> for more information on style sheets. 6.9. How do I indent a lot of text? Use a style sheet to set a left margin for the whole document or part of it: /* Entire document */ BODY { margin-left: 20% } /* Part of a document with CLASS="foo" */ .foo { margin-left: 15% } See <URL:http://www.htmlhelp.com/reference/css/> for more information on style sheets. 6.10. How do I do a page break? Page breaks are offered in Cascading Style Sheets, Level 2, but they are not well supported by browsers. See <URL:http://www.w3.org/TR/REC-CSS2/page.html#page-breaks> for information on CSS2 page breaks. In general, page breaks are not appropriate on the Web since what makes a nice page break for you with your font and font size may be a poor page break for me with my font and font size. If you need to produce a nicely formatted printed copy of your HTML documents, you might also consider using special purpose tools rather than your browser's Print function. For example, html2ps generates nicely formatted PostScript output from HTML documents, and HTML Scissor uses special HTML comments for suggesting page breaks. 6.11. How do I have a fixed background image? Use a style sheet with the following ruleset: body { color: black; background: white url(foo.gif) fixed } Note that the fixed property used in the above style sheet is supported by Internet Explorer 3+, Netscape Navigator 5+, and other browsers. In contrast, the proprietary BGPROPERTIES=fixed attribute is supported only by Internet Explorer 3+. 6.12. How do I have a non-tiled background image? Use a style sheet with the following ruleset: body { color: black; background: white url(foo.gif) no-repeat } 6.13. How can I have a custom icon when people bookmark my site? This is a feature introduced by Internet Explorer 5.x. By default, the browser requests an file named "favicon.ico" at the same base URL as the document being bookmarked. If it doesn't find this file, then it will try again in the root directory of your site. Web authors can specify a different path for the icon file with a <LINK> element like this: <LINK REL="SHORTCUT ICON" HREF="/pathname/filename.ico"> The image should be 16 by 16 pixels, in the Windows icon format. If your graphics program doesn't support the Windows icon format, you can use a tool like the free Java-based icon generator at <URL:http://www.favicon.com/> to convert/create your icon. For further information, search for "favicon.ico" at <URL:http://msdn.microsoft.com/workshop/essentials/versions/ICPIE5.asp>. 7. HTML Forms 7.1. How do I use forms? The basic syntax for a form is: <FORM ACTION="[URL]">...</FORM> When the form is submitted, the form data is sent to the URL specified in the ACTION attribute. This URL should refer to a server-side (e.g., CGI) program that will process the form data. The form itself should contain * at least one submit button (i.e., an <INPUT TYPE="submit" ...> element), * form data elements (e.g., <INPUT>, <TEXTAREA>, and <SELECT>) as needed, and * additional markup (e.g., identifying data elements, presenting instructions ) as needed. A more detailed explanation of the use of forms is available at <URL:http://www.hut.fi/u/jkorpela/forms/>. If you want to install CGI programs on your server, the following are useful resources: * the CGI Programming FAQ <URL:http://www.htmlhelp.com/faq/cgifaq.html> * the CGI section of the W3C's Security FAQ <URL:http://www.w3.org/Security/faq/wwwsf4.html> * the list of prewritten CGI scripts/programs at <URL:http://www.cgi-resources.com/Programs_and_Scripts/> 7.2. How do I get form data emailed to me? The only reliable mechanism for processing form submissions is with a server-side (e.g., CGI) program. To send form data to yourself via email, you should use a server-side program that processes the form submission and sends the data to your email address. Some web service providers make standard form-to-email programs available to their customers. Check with your service provider for details. If you can install CGI programs on your own server, see the answer to the previous question for a list of useful resources. If you can't run CGI programs on your own server, you can use a remotely hosted form-to-email services. A list of such services can be found at <URL:http://www.cgi-resources.com/Programs_and_Scripts/Remotely_Hosted/Form_Pro cessing/>. Note that the provider of a remotely hosted service will have access to any dat a submitted via the service. Forms that use ACTION="mailto:..." are unreliable. They may work for some of your users, but they will fail for others who have different software configurations. 7.3. How do I make a form so it can be submitted by hitting ENTER? The short answer is that the form should just have one <INPUT TYPE=TEXT> and no TEXTAREA, though it can have other form elements like checkboxes and radio buttons. For a more detailed answer, see <URL:http://ppewww.ph.gla.ac.uk/%7Eflavell/www/formquestion.html>. 7.4. How can I make a form with custom buttons? Rather than a normal submit button (<INPUT TYPE=submit ...>), you can use an image of a custom submit button. Use <INPUT NAME=Send TYPE=image SRC="http://url.to/image.gif" ALT="Send" VALUE="Send">. Most browsers will also send the x and y coordinates of the location where the user clicked on the imag e to the server. They are available as "Send.x=000&Send.y=000" in the CGI input. For more information, see <URL: http://ppewww.ph.gla.ac.uk/%7eflavell/www/trysub.html>. For the reset button, one could use <BUTTON TYPE=reset ...>, JavaScript, and/or style sheets, although none of these mechanisms work universally. For more information, see <URL:http://www.hut.fi/u/jkorpela/forms/imagereset.html>. 7.5. Can I have two or more Submit buttons in the same form? Sure. This is part of HTML 2.0 Forms support (some early browsers did not support it, but browser coverage is now excellent). You will need to give your Submit buttons a Name attribute, and, optionally, a Value attribute. In order to determine which button was used, you will want to use distinctive Names, or Values, or both. Browsers will display the Value, in addition to sending it to the server, so choose something that's meaningful to the user. Example: <INPUT TYPE=SUBMIT NAME=join VALUE="I want to join now"> -or- <INPUT TYPE=SUBMIT NAME=info VALUE="Please send full details"> If you're unsure what results you're going to get when you submit your form, NCSA has a standard script which you can use. Code this, for example (assuming method "post"): <form method="post" action="http://hoohoo.ncsa.uiuc.edu/htbin-post/post-query"> and then go through the motions of submitting your form. The NCSA server decode s the form input, and displays the result to you. 7.6. How can I allow file uploads to my web site? First of all, the RFC for this is located at <URL:http://www.ics.uci.edu/pub/ietf/html/rfc1867.txt>. File upload is handled by the CGI.pm Perl5 library available from <URL:http://stein.cshl.org/WWW/software/CGI/cgi_docs.html>. The most recent versions of the cgi-lib.pl library also support file upload. These things are necessary for Web-based uploads: * An HTTP server that accepts uploads. * Access to the /cgi-bin/ to put the receiving script. * A form implemented something like this: <form method="POST" enctype="multipart/form-data" action="fup.cgi"> File to upload: <input type=file name=upfile><br> Notes about the file: <input type=text name=note><br> <input type=submit value=Press> to upload the file! </form> Not all browsers support form-based file upload, so try to give alternatives where possible. Also, if you need to do file upload in conjunction with form-to-email, the Perl package MIME::Lite handles email attachments. 7.7. How can I use forms for pull-down navigation menus? There is no way to do this in HTML only; something else must process the form. JavaScript processing will work only for readers with JavaScript-enabled browsers. CGI and other server-side processing is reliable for human readers, but search engines have problems following any form-based navigation. See <http://www.hut.fi/u/jkorpela/forms/navmenu.html>, which explains how to create pull-down menus, as well as some better navigation alternatives. 8. HTML Frames 8.1. How do I make a link or form in one frame update another frame? In the frameset document (the HTML document containing the <FRAMESET> and <FRAME> elements), make sure to name the individual frames using the NAME attribute. The following example creates a top frame named "navigation" and a bottom frame named "content": <FRAMESET ROWS="*,3*"> <FRAME NAME="navigation" SRC="navigation.html"> <FRAME NAME="content" SRC="content.html"> <NOFRAMES><BODY>  </BODY></NOFRAMES> </FRAMESET> Then, in the document with the link, use the TARGET attribute to specify which frame should be used to display the link. (The value of the TARGET attribute should match the value of the target frame's NAME attribute.) You can specify the target frame for a link (e.g., <A TARGET="content" HREF=...>) or for a form (e.g., <FORM TARGET="content" ACTION=...>). Also, you can use <BASE TARGET=...> to change the default target frame for the entire document (normally, the default target frame is "_self", the current frame). 8.2. Why do my links open new windows rather than update an existing frame? If there is no existing frame with the name you used for the TARGET attribute, then a new browser window will be opened, and this window will be assigned the name you used. Furthermore, TARGET="_blank" will open a new, unnamed browser window. In HTML 4.0, the TARGET attribute value is case-insensitive, so that abc and AB C both refer to the same frame/window, and _top and _TOP both have the same meaning. However, most browsers treat the TARGET attribute value as case-sensitive and do not recognize ABC as being the same as abc, or _TOP as having the special meaning of _top. 8.3. How do I update two frames at once? There are two basic techniques for updating multiple frames with a single link: The HTML-based technique links to a new frameset document that specifies the ne w combination of frames. The JavaScript-based solution uses the onClick attribute of the link to update the additional frame (or frames). The HTML-based technique can link to a new frameset document with TARGET="_top" (replacing the entire frameset), but there is an alternative if the frames to b e updated are part of a nested frameset. In the initial frameset document, use a secondary frameset document to define the nested frameset. For example: <FRAMESET COLS="*,3*"> <FRAME SRC="contents.html" NAME="Contents"> <FRAME SRC="frameset2.html" NAME="Display"> </FRAMESET> A link can now use TARGET="Display" to replace simultaneously all the frames defined by frameset2.html. The JavaScript-based solution uses the onClick attribute of the link to perform the secondary update. For example: <A HREF="URL1" TARGET=Frame1 onClick="top.Frame2.location='URL2';">Update frames</A> The link will update Frame1 with URL1 normally. If the reader's browser support s JavaScript (and has it enabled), then Frame2 will also be updated (with URL2). 8.4. How do I get out of a frameset? If you are the author, this is easy. You only have to add the TARGET attribute to the link that takes readers to the intended 'outside' document. Give it the value of _top. In many current browsers, it is not possible to display a frame in the full browser window, at least not very easily. The reader would need to copy the URL of the desired frame and then request that URL manually. I would recommend that authors who want to offer readers this option add a link to the document itself in the document, with the TARGET attribute set to _top s o the document displays in the full window if the link is followed. 8.5. How do I make sure my framed documents are displayed inside their frameset ? When the sub-documents of a frameset state are accessed directly, they appear without the context of the surrounding frameset. If the reader's browser has JavaScript support enabled, the following script will restore the frameset: <SCRIPT TYPE="text/javascript">  </SCRIPT> A more universal approach is a "restore frames" link: <A HREF="frameset.html" TARGET="_top">Restore Frames</A> Note that in either case, you must have a separate frameset document for every content document. If you link to the default frameset document, then your reade r will get the default content document, rather than the content document he/she was trying to access. These frameset documents should be generated automatically, to avoid the tedium and inaccuracy of creating them by hand. Note that you can work around the problem with bookmarking frameset states by linking to these separate frameset documents using TARGET="_top", rather than linking to the individual content documents. 8.6. Is there a way to prevent getting framed? "Getting framed" refers to having your documents displayed within someone else' s frameset without your permission. This can happen accidentally (the frameset author forgot to use TARGET="_top" when linking to your document) or intentionally (the frameset author wanted to display your content with his/her own navigation or banner frames). To avoid "framing" other people's documents, you must add TARGET="_top" to all links that lead to documents outside your intended scope. Unfortunately, there is no reliable way to specify that a particular document should be displayed in the full browser window, rather than in the current frame. If you can configure your server to send the proprietary header Window-Target: _top in the HTTP response, then Netscape browsers will display your document in the full browser window. However, other browsers ignore this header, and it doesn't work to use <META HTTP-EQUIV="Window-target" CONTENT="_top"> in the document itself to mimic the HTTP response. Another workaround is to use <BASE TARGET="_top"> in the document, but this onl y specifies the default target frame for links in the current document, not for the document itself. If the reader's browser has JavaScript enabled, the following script will automatically remove any existing framesets: <SCRIPT TYPE="text/javascript">  </SCRIPT> An alternative script is <SCRIPT TYPE="text/javascript">  </SCRIPT> </HEAD> <BODY onLoad="breakOut()"> 8.7. How do I specify a specific combination of frames instead of the default document? This is unfortunately not possible. When you navigate through a site using frames, the URL will not change as the documents in the individual frames change. This means that there is no way to indicate the combination of document s that make up the current state of the frameset. The author can provide and link to multiple frameset documents, one for each combination of frame content. These frameset documents can be generated automatically, possibly even being created on the fly by a CGI program. 8.8. How do I remove the border around frames? Removing the border around frames involves both not drawing the frame borders and eliminating the space between the frames. The two major frames-capable browsers use different proprietary attributes to achieve this. Netscape recognizes the BORDER attribute on FRAMESET. It can be set to 0, in which case the border will not be shown, and the spacing will be set to zero. Microsoft Internet Explorer recognizes the FRAMEBORDER and FRAMESPACING attributes on FRAMESET, but in some versions also on FRAME for individual frames. Both attributes must be set to 0. So, the most widely supported way to display borderless frames is <FRAMESET ... BORDER=0 FRAMEBORDER=0 FRAMESPACING=0>. Note that these attributes are proprietary and not part of the HTML 4.0 specification. Also, removing the border around a frame makes it impossible to resize it, as this border is also used in most GUIs to change the size of the window. 8.9. How do I change the title of a framed document? The title displayed is the title of the frameset document rather than the title s of any of the pages within frames. To change the title displayed, link to a new frameset document using TARGET="_top" (replacing the entire frameset). 8.10. Why aren't my frames the exact size I specified? Netscape Navigator seems to round pixel-based frame dimensions to the nearest whole percentage, and to use those percentage-based dimensions when laying out the frames. Thus, frames with pixel-based dimensions will be rendered with a slightly different size than that specified in the frameset document. There is no way to prevent this behavior, and the rounding error will vary depending on the exact size of the browser window. To accomodate this, you should design your site to adapt to variations in the browser's presentation. This is a good idea in general, but especially so in this situation. 8.11. Are there any problems with using frames? The fundamental problem with the design of frames is that framesets create states in the browser that are not addressable. Once any of the frames within a frameset changes from its default content, there is no longer a way to address the current state of the frameset. It is difficult to bookmark - and impossible to link or index - such a frameset state. It is impossible to reference such a frameset state in other media. When the sub-documents of such a frameset state are accessed directly, they appear without the context of the surrounding frameset. Basic browser functions (e.g., printing, moving forwards/backwards in the browser's history) behave differently with framesets. Furthermore, frames focus on layout rather than on information structure, and many authors of framed sites neglect to provide useful alternative content in the <NOFRAMES> element. Both of these factors cause accessibility problems for browsers that differ significantly from the author's expectations and for searc h engines. For further discussion, see <URL:http://www.htmlhelp.com/design/frames/whatswrong.html> ------------------------------------------------------------ For additions or omissions to this FAQ, please contact <darin@htmlhelp.com>. All information contained herein was originally compiled by members of the Web Design Group, principally Arnoud "Galactus" Engelfriet, John Pozadzides, and Darin McGrew. Additional input has been provided by Boris Ammerlaan, Lori Atwater, Alex Bell, Stan Brown, Roger Carbol, Alex Chapman, Jan Roland Eriksson, Jon Erlandson, Mar k Evans, Alan Flavell, Lucie Gelinas, Bjoern Hoehrmann, Tina Marie Holmboe, Peter Jones, Nick Kew, Jukka Korpela, Simon Lee, Nick Lilavois, Neal McBurnett, Glen McDonald, Dan McGarry, Ken O'Brien, Timothy Prodin, Steve Pugh, Liam Quinn, Colin Reynolds, Kai Sch�tzl, Doug Sheppard, Sue Sims, Toby Speight, Warren Steel, Ian Storms, Peter Thomson, Daniel Tobias, and Diane Wilson. Thanks everyone! ------------------------------------------------------------ Web Design Group Copyright � 1996-1999. All rights reserved.