Techniques for Web Content Accessibility Guidelines 1.0

W3C Working Draft 12-April-1999

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Wendy Chisholm <chisholm@trace.wisc.edu>
Gregg Vanderheiden <gv@trace.wisc.edu>
Ian Jacobs <ij@w3.org>


This document is a list of techniques that implement the checkpoints defined in "Web Content Accessibility Guidelines 1.0".

While Web Content Accessibility Guidelines 1.0 strives to be a stable document (as a W3C Recommendation), the current document will undoubtedly evolve as technologies change and content developers discover more effective techniques for designing accessible pages.

This document is part of a series of accessibility documents published by the Web Accessibility Initiative.

Status of this document

This is a W3C Working Draft for review by W3C members and other interested parties. It is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". This is work in progress and does not imply endorsement by, or the consensus of, either W3C or members of the Web Content Guidelines Working Group.

This draft of the document comes during the Propose Recommendation period of the "Web Content Accessibility Guidelines 1.0". This is the first time the current document "stands on its own", i.e., is not closely associated with the associated guidelines.

This document has been produced as part of the W3C Web Accessibility Initiative. The goal of the Web Content Guidelines Working Group is discussed in the Working Group charter.

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR.

Please send detailed comments on this document to w3c-wai-gl@w3.org.

Table of Contents

1 Priorities

Each checkpoint has a priority level assigned by the Working Group based on the checkpoint's impact on accessibility.

[Priority 1]
A Web content developer must satisfy this checkpoint. Otherwise, one or more groups will find it impossible to access information in the document. Satisfying this checkpoint is a basic requirement for some groups to be able to use Web documents.
[Priority 2]
A Web content developer should satisfy this checkpoint. Otherwise, one or more groups will find it difficult to access information in the document. Satisfying this checkpoint will remove significant barriers to accessing Web documents.
[Priority 3]
A Web content developer may address this checkpoint. Otherwise, one or more groups will find it somewhat difficult to access information in the document. Satisfying this checkpoint will improve access to Web documents.

Some checkpoints specify a priority level that may change under certain (indicated) conditions.

The checkpoints in this document are numbered to match their numbering in Web Content Accessibility Guidelines 1.0.

2 How the Techniques are Organized

This document is a list of techniques that implement the checkpoints defined in "Web Content Accessibility Guidelines 1.0". This document is organized as follows:

Accessibility Themes
This section introduces some general techniques to promote accessibility that are independent of any specific markup language.
HTML Techniques
This section explains how to implement applicable checkpoints in HTML (refer to [HTML40], [HTML32]) and includes numerous practical examples. To complement this section, an index of HTML elements and attributes provides information about all elements of HTML 4.0 and all attributes that affect accessibility directly. For each element, the index includes links to techniques that refer to it.
CSS Techniques
This section explains how to implement applicable checkpoints in CSS1 and CSS2 (refer to [CSS1], [CSS2]).
XML Techniques
This section explains how to implement applicable checkpoints in XML 1.0 (refer to [XML]).

A checkpoint map has been provided for navigation of the techniques. For each checkpoint, the map includes its definition (as it appears in the "Web Content Accessibility Guidelines 1.0") and links to applicable techniques for the checkpoint. In addition, the beginning of each section of this document lists the checkpoints that are addressed in that section.

3 Accessibility Themes

The following sections discuss some accessibility themes that Web content developers should keep in mind as they design documents and sites.

3.1 Structure vs. Presentation

When designing a document or series of documents, content developers should strive first to identify the desired structure for their documents before thinking about how the documents will be presented to the user. Distinguishing the structure of a document from how the content is presented offers a number of advantages, including improved accessibility, manageability, and portability.

Identifying what is structure and what is presentation may be a challenging task at times that content developers must develop a mindset for recognizing. For instance, many content developers consider that a horizontal rule (the HR element) communicates a structural division. This may be true for sighted users, but to unsighted users or users without graphical browsers, a horizontal rule has next to no meaning (One might "guess" that an HR element implies a structural division, but without other information, there is no guarantee.) In HTML, content developers should use the HTML 4.0 header elements (H1-H6) to identify new sections. These may be complemented by visual or other cues such as horizontal rules, but should not be replaced by them.

The inverse holds as well: content developers should not use structural elements to achieve presentation effects. For instance in HTML, even though the BLOCKQUOTE element may cause indented text in some browsers, that is not its meaning, only a presentation side-effect. BLOCKQUOTE elements used for indentation confuse users and search robots alike, who expect the element to be used to mark up block quotations.

The separation of presentation from structure in XML documents is inherent. As Norman Walsh states in "A Guide to XML" [WALSH],

"HTML browsers are largely hardcoded. A first level heading appears the way it does because the browser recognizes the H1 tag. Again, since XML documents have no fixed tag set, this approach will not work. The presentation of an XML document is dependent on a stylesheet."

Quicktest! To determine if content is structural or presentational, create an outline of your document. Each point in the hierarchy denotes a structural change. Use structural markup to mark these changes and presentational markup to make them more apparent visually and aurally. Notice that horizontal rules will not appear in this outline and therefore are not structural, but presentational.

Note. This test only looks at the structure at the chapter and paragraph level. To determine structure within phrases, look for abbreviations, changes in natural language, definitions, and list items.

3.2 Text equivalents

Checkpoints in this section: 1.1, 1.2, 3.8, 1.5, 13.10, 3.3, and 12.1, and 12.2.

Text is considered accessible to almost all users since it may be handled by screen readers, non-visual browsers, braille readers, displayed visually, magnified, synchronized with a video to create a caption, etc. It is good practice, as you design a document containing non-textual information (images, graphics, applets, sounds, etc.) to think about supplementing that information with textual equivalents wherever possible.

A text equivalent describes the function or purpose of content. For complex content (charts, graphs, etc.), the text equivalent may be longer and include descriptive information.

Text equivalents should be provided for logos, photos, submit buttons, applets, bullets in lists, ascii art, and all of the links within an image map as well as invisible images used to layout a page.

Quicktest! A good test to determine if a text equivalent is useful is to imagine reading the document aloud over the telephone. What would you say upon encountering this image to make the page comprehensible to the listener?

3.2.1 Overview of technologies

How one specifies a text equivalent depends on the document language.

For example, depending on the element, HTML allows content developers to specify text equivalents through attributes ("alt" or "longdesc" ) or in element content (the OBJECT element).

Video formats, such as Quicktime, will allow developers to include a variety of alternative audio and video tracks. SMIL, will allow developers to synchronize alternative audio and video clips, and text files with each other.

In creating XML DTDs, ensure that elements that might need a description have some way of associating themselves with the description.

Some image formats allow internal text in the data file along with the image information. If an image format supports such text (e.g., Portable Network Graphics, see [PNG]) content developers may also supply information there as well.

3.2.2 Backward Compatibility

Since some user agents do not support new HTML 4.0 attributes or if a person is using an older video player, or whatever technology compatibility exists, here are some alternatives to the above solutions. Methods include:

3.3 Alternative pages

Checkpoints in this section: 11.4, and 6.5.

Although it is possible to make most content accessible, it may happen that all or part of a page remains inaccessible. Additional techniques for creating accessible alternatives include:

  1. Allow users to navigate to a separate page that is accessible and maintained with the same frequency as the inaccessible original page.
  2. Instead of static alternative pages, set up server-side scripts that generate accessible versions of a page on demand.
  3. Refer to the examples for Frames and Scripts.
  4. Provide a phone number, fax number, e-mail, or postal address where information is available and accessible, preferably 24 hours a day

There are several techniques for linking to an accessible alternative page:

  1. Provide links at the top of both the main and alternative pages to allow a user to move back and forth between them. For example, at the top of a graphical page include a link to the text-only page, and at the top of a text-only page include a link to the associated graphical page. Ensure that these links are one of the first that users will tab to by placing them at the top of the page, before other links.
  2. Use meta information to designate alternative documents. Browsers should load the alternative page automatically based on the user's browser type and preferences. For example, in HTML, use the LINK element as follows:


    User agents that support LINK will load the alternative page for those users whose browsers may be identified as supporting "aural","braille", or "tty" rendering.

            <TITLE>Welcome to the Virtual Mall!</TITLE>
            <LINK title="Text-only version"
                  media="aural, braille, tty">

    End example.

3.4 Keyboard access

Checkpoints in this section: 9.2.

Not every user has a graphic environment with a mouse or other pointing device. Some users rely on keyboard, alternative keyboard or voice input to navigate links, activate form controls, etc. Content developers should always ensure that users may interact with a page with devices other than a pointing device. A page designed for keyboard access (in addition to mouse access) will generally be accessible to users with other input devices. What's more, designing a page for keyboard access will usually improve its overall design as well.

Keyboard access to links and form controls may be specified in a few ways:

Image map links
Provide text equivalents for client-side image map areas, or provide redundant text links for server-side image maps. Refer to the image map section for examples.
Keyboard shortcuts
Keyboard shortcuts allow users to combine keystrokes to navigate links or form controls on a page. Note. Keyboard shortcuts may be handled differently by different operating systems. The primary difference being which keys to press to activate the shortcut. On Windows machines, the "alt" and "ctrl" key are most commonly used while on a Macintosh, it is the apple or "clover leaf" key. Refer to the Keyboard access for links and Keyboard Access to Forms sections for examples.
Tabbing order
Tabbing order describes a (logical) order for navigating from link to link or form control to form control (usually by pressing the "tab" key, hence the name). Refer to the Keyboard Access to Forms section for examples.

3.4.1 Device-independent control for embedded interfaces

Some elements import objects whose interfaces cannot be controlled through the markup language. For example, in HTML, applets, and multi-media players. In such cases, users should ensure that if the imported objects themselves do not provide accessible interfaces, that an alternative does.

3.5 Navigation

Checkpoints in this section: 14.3, 13.4, 13.8 13.5, 13.3, 13.7, and 13.2.

A consistent style of presentation on each page allows users to easily find navigation buttons between pages, as well as find the primary content for each page. While this helps make it easier for everyone, it especially benefits people with learning and reading disabilities. Making it easy to predict where the needed information is found on each page will increase the likelihood that it will be found.

Examples of structures that may appear at the same place between pages:

  1. navigation bars
  2. the primary content of a page
  3. advertising

A navigation structure is the set of possible paths available for a user to take through the content on your site. Providing navigation bars, site maps, and search features all increase the likelihood that a user will navigate easily to the information that they seek on your site. If your site is highly visual in nature, the structure might be harder to navigate through if the user can't form a mental map of where they are going or where they have been. Therefore, provide a description that will help users discover the mechanisms you have provided.

Content developers should use link types (reference to HTML 4.0, 6.12) with LINK so that user agents may use build navigation structures. (Provide example with "next", "prev", "content", and "start").

See also the section on links.

3.6 Comprehension

Checkpoints in this section: 14.1, 14.2, and 12.3.

  1. Provide a simplified text equivalent as an alternative to the primary text. This may be helpful to non-readers and people who have difficulty reading. Non-readers can hear the simplified text using speech output technology. Individuals with reading difficulties may be able to read the simplified text. Because of the challenges of maintaining separate texts, it is preferable to simplify only the main text and not provide a simplified text equivalent.
  2. Visual, non-text equivalents may include, for example graphics, animations, or videos. These are especially helpful for non-readers who can perceive visual presentations. For example, sighted deaf non-readers may benefit from video equivalents in manual communication (sign language). Non-readers, whether they have disability or not, may also benefit from highly graphical equivalents.

    Non-visual, non-text equivalents are very diverse. Among the most common are pre-recorded audio of music, spoken language, or sound effects. Such equivalents would be especially important for non-readers who can perceive audio presentations. Presentations in the audio medium of synthesized speech and the tactile medium of braille are usually derived from text or text equivalents so usually require no additional work from the developer.

Follow these writing suggestions:

Because people tend to scan rather than read Web pages, the quality of headings is particularly important. Good headings will at least get people to a section that has the information they need. From there they can go to a dictionary or even print out a section and ask for help.

Grouping mechanisms in HTML 4.0 include:

All of these grouping mechanisms should be used when appropriate and natural, i.e., when the information lends itself to logical groups. Content developers should not create groups randomly, as this will confuse all users.

3.7 Content negotiation

Checkpoints in this section: 11.3.

  1. Instead of including links such as "Here is the French version of this document", use content negotiation so that the French version is served to clients requesting French versions of documents.
  2. If not possible to use content negotiation, in HTML use "type" and "hreflang".

3.8 Automatic page refresh

Checkpoints in this section: 7.4, and 7.5.

Content developers sometimes create pages that refresh or change without the user requesting the refresh. This automatic refresh can be very disorienting to some users. There are two types of refresh mechanisms commonly used.

This type of refresh changes the user's page at regular intervals. This might be accomplished by the following HTML markup:

Deprecated example.

<META http-equiv="refresh" content="60">

Content developers should not use this technique to simulate "push" technology. Developers cannot predict how much time a user will require to read a page; premature refresh can disorient users. Content developers should avoid periodic refresh and allow users to choose when they want the latest information.

Automatic forwarding redirects the user from one page to another generally after a timeout. The following HTML markup with META is frequently used to achieve this effect:

Deprecated example.

<TITLE>Don't use this!</TITLE>
<META http-equiv="refresh" content="5; 
<P>If your browser supports Refresh, 
you'll be transported to our 
<A href="http://www.acme.com/newpage">new site</A>
in 5 seconds, otherwise, select the link manually.

However, users should not redirect users with this markup since is non-standard, it disorients users, and it can disrupt a browser's history of visited pages. Instead, in order of preference, authors should:

  1. Configure the server to use the appropriate HTTP status code (301). Using HTTP headers is preferable because it reduces Internet traffic and download times, it may by applied to non-HTML documents, and it may be used by agents who requested only a HEAD request (e.g., link checkers). Also, status codes of the 30x type provide information such as "moved permanently" or "moved temporarily" that cannot be given with META refresh.
  2. Replace the page that would be redirected with a static page containing a normal link to the new page.

Note. Both checkpoint 7.4 and checkpoint 7.5 address problems posed by legacy user agents. Newer user agents should disable refresh and substitute a link to new information at the top of the page.

3.9 Other topics

Checkpoints in this section: 7.1 and 13.9.

A flickering or flashing screen may cause seizures in users with photosensitive epilepsy. Seizures can be triggered by flickering or flashing in the 4 to 59 flashes per second (Hertz) range with a peak sensitivity at 20 flashes per second as well as quick changes from dark to light (like strobe lights).

For example, Indicate which is the first page of the document and which page follows the current one. (e.g., by using the LINK element).

3.10 Validation

This section discusses strategies and techniques for testing Web documents to determine what accessibility issues have been resolved or which still exist. The key thing to remember in each of these testing scenarios is that often-times we are merely replicating a condition caused by a disability but not the disability itself. Therefore, as you read your page with images not loaded in a graphical browser, you still may look at it, or you may turn your monitor off, but will be able to turn it back on again. Since we are not recreating the experience of having a disability people might still find your page less usable than you had expected. This is also why one of the strategies is to observe people with varying disabilities use your page.

These tests should highlight major access issues, however and are valuable in reducing the number of issues a page might have.

3.10.1 Automatic validators

Tools that automatically check source code are useful in that they can quickly scan your whole site and, based on syntax, tell you where issues exist or potentially exist. Since automatic checkers consist of a series of rules, they may only check the syntax. Therefore, your syntax may be correct, but you could still have access problems. For example, an automatic checker can determine that you have alternative text, but it can not determine if it is appropriate. Therefore, some checkers will ask you questions and step you through more subjective parts of the analysis.

  1. Use an automated accessibility validation tool such as Bobby (refer to [BOBBY]).
  2. Use an HTML validation service such as the W3C HTML Validation Service (refer to [HTMLVAL]).
  3. Use a style sheets validation service such as the W3C CSS Validation Service (refer to [CSSVAL]).

3.10.2 Repair tools

Validators usually report what issues to solve and often give examples of how to solve them, however they usually do not help an author walk through each problem and help the author modify the code on the fly. The WAI Evaluation and Repair Working Group ([WAI-ER]) is working to develop a suite of tools that will help authors not only identify issues but solve them as well.

3.10.3 User scenarios

Keep in mind that most user agents (browsers) and operating systems allow users to configure settings that change the way software looks, sounds, and behaves. With the variety of user agents, different users will have very different experiences with the Web.

  1. Test your pages with a text-only browser such as Lynx ([LYNX]) or a Lynx emulator such as Lynx Viewer ([LYNXVIEW]) or Lynx-me ([LYNXME]).
  2. Use multiple graphic browsers, with: sometimes changing these settings is a matter of toggling a button in one of the main menu on or off, or a control on the page, other times it may require searching a few layers into user setting dialogs to find a way to change the presentation.
  3. Use several browsers, old and new. Beware that some browsers only allow one version of themselves to be installed on a machine at a time. Therefore, it is good to have a test machine with older version running. It is also hard sometimes to find older versions of browsers.
  4. Use a self-voicing browser (pwwebspeak, IBM Home page Reader), a screen reader (Henter Joyce's JAWs, Artic's WinVision, etc.), magnification software (Opera performs magnification, as does ...) , a small display (such as on a PDA, or in x by y resolution), onscreen keyboard, alternative keyboard, read2me.

3.10.4 Spell and grammar checks

A person reading a page with a speech synthesizer may not be able to decipher the synthesizer's best guess for a word with a spelling error. Grammar checkers will help to ensure that the textual content of your page is correct. This will help readers for whom your document is not written in their native tongue, or people who are just learning the language of the document. Thus, you will help increase the comprehension of your page.

3.10.5 Passing the tests

Passing all of these test does not guarantee at this time that your page is a "triple-A" site. If you are able to check all of the checkpoints in the checklist, then you should be able to call your site "Triple-A." Please refer to the checkpoint checklist and discussion of conformance for more information.

If, after completing these tests and adjusting your design accordingly, you find that your page is still not accessible, you must create an alternative page that is accessible.

3.11 Browser Support

Checkpoints in this section: 11.1.

  1. In general, user agents ignore HTML attributes they don't support and they render the content of unsupported elements.

At the time of this writing, several of the latest HTML 4.0 attributes that may significantly increase accessibility of Web pages have not been implemented in user agents. Therefore, authors may be asking

  1. Why should I use these attributes or elements if they aren't supported?
  2. Will using these attributes or elements break my pages as they are displayed today?
  3. How will I know when to use these features if they aren't supported today?
  4. Which browsers support these features? Which don't?

There are also other issues with backward compatibility. We require that pages transform gracefully across browsers, but how can one author test all possible browser and user scenarios? Therefore, there must be some "least common denominator" that we can design for?

Since the data about who is accessing the Web and with which tools is derived from people's best guesses and self-selected surveys, we have no definitive answers. However, we can help authors look at the data for themselves to decide what decision they want to make.

3.11.1 References for Browser Support

Although this site has been collecting data on browser capabilities for a number of years, the last update of their data occurred on 15 April, 1999. However, this includes some data for the early releases of the 4.0 versions of Internet Explorer and Netscape, as well as other browsers in use at the time. The goal of the site is to allow developers to find information on the capabilities of a specific browser as well as identify which browsers support a certain feature of HTML. The keepers of the site expect to start updating their data in the near future. [BROWSERCAPS]
webreview.com offers a few browser compatibility charts, including the "safe list" and the "danger list." They also offer several helpful articles about designing style sheets. [WEBREVIEW]

3.11.2 Statistics on Web usage

4 HTML Techniques

The following sections list some techniques for using HTML (and some CSS) to design accessible documents and some techniques for avoiding HTML accessibility traps. The sections are organized by topic (and mirror the organization of the HTML 4.0 specification, [HTML40]).

4.1 Document structure and metadata

Checkpoints in this section: 3.2

As discussed above, content developers should use structural markup wherever possible (and use it as intended by the authors of W3C specifications). Structural elements promote consistency in documents and supply information to other tools (e.g., indexing tools, search engines, programs that extract tables to databases, navigation tools that use header elements, and automatic translation software that translates text from one language into another.

4.1.1 Metadata

Some structural elements provide information about the document itself. This is called "metadata" about the document -- Metadata is information about data. Well-crafted metadata can provide important orientation information to users. HTML elements that provide useful information about a document include:

4.1.2 Section headers

Checkpoints in this section: 3.5.

Sections should be introduced with the HTML header elements (H1-H6). Other markup may complement these elements to improve presentation (e.g., the HR element to create a horizontal dividing line), but visual presentation is not sufficient to identify document sections.

Since some users skim through a document by navigating its headings, it is important to use them appropriately to convey document structure. Users should order heading elements properly. For example, in HTML, H2 elements should follow H1 elements, H3 elements should follow H2 elements, etc. Content developers should not "skip" levels (e.g., H1 directly to H3). Do not use headings to create font effects; use style sheets to change font styles.

Note that in HTML, heading elements (H1 - H6) do not contain entire logical sections in their content. They should be used to begin a section of a document. The following HTML markup shows how to create a true document "section" and control its appearance with style sheets:


   <TITLE>Cooking techniques</TITLE>
   <STYLE type="text/css">
      /* Indent the entire section */
      DIV.section2 { margin-left: 5% }
   <H1>Cooking techniques</H1>
   ... some text here ...
   <DIV class="section2">
   <H2>Cooking with oil</H2>
   ... text of the section ...

   <DIV class="section2">
   <H2>Cooking with butter</H2>
   ... text of the next section ...

End example.

4.2 Language information

Checkpoints in this section: 4.1, and 4.3.

If you use a number of different languages on a page, make sure that any changes in language are clearly identified by using the "lang" attribute:


   <P>And with a certain <SPAN lang="fr">je ne sais quoi</SPAN>, 
   she entered both the room, and his life, forever. <Q>My name
   is Natasha,</Q> she said. <Q lang="it">Piacere,</Q>
   he replied in impeccable Italian, locking the door.

End example.

It is also good practice to identify the primary language of a document.


    <HTML lang="fr">
       ....rest of an HTML document written in French...

End example.

4.3 Text markup

As mentioned above, structural elements add information to a page that may be used by browsers, search engines, and other software. Content developers are encouraged to use structural elements and attributes whenever possible (refer to the index of HTML elements and attributes). Below we discuss how to further improve accessibility by careful use of attributes with these elements.

4.3.1 Emphasis

The proper HTML elements should be used to mark up emphasis: EM and STRONG. The B and I elements should not be used; they are used to create a visual presentation effect. The EM and STRONG elements were designed to indicate structural emphasis that may be rendered in a variety of ways (font style changes, speech inflection changes, etc.)

4.3.2 Acronyms and abbreviations

Checkpoints in this section: 4.2.

Mark up abbreviations and acronyms with ABBR and ACRONYM and use "title" to indicate the expansion:


   <P>Welcome to the <ACRONYM title="World Wide Web">WWW</ACRONYM>!

End example.

4.3.3 Quotations

The Q and BLOCKQUOTE elements mark up inline and block quotations, respectively.

Checkpoints in this section: 3.7.

Refer to the language example above for an illustration of the ACRONYM element.


This example marks up a longer quotation with BLOCKQUOTE:

   <BLOCKQUOTE cite="http://www.shakespeare.com/loveslabourlost">
     <P>Remuneration! O! that's the Latin word for three farthings.
        --- William Shakespeare (Love's Labor Lost).

End example.

4.3.4 Miscellaneous structural markup

The HTML 4.0 specification defines the following structural elements for miscellaneous markup needs:

Contains a citation or a reference to other sources.
Indicates that this is the defining instance of the enclosed term.
Designates a fragment of computer code.
Designates sample output from programs, scripts, etc.
Indicates text to be entered by the user.
Indicates an instance of a variable or program argument.
Indicates text inserted into a document.
Indicates text deleted from a document.

4.3.5 Text markup rather than images

Checkpoints in this section: 3.1.

The section on images discusses the need for images to have text equivalents - in order to be interpreted by people who cannot see or who have support for images turned off. There are other reasons to use markup rather than images:

  1. If style sheets are used instead, words may be magnified or read with a screen reader.
  2. Words may be searched by a search engine.
  3. Mathematical equations won't require an elaborate text equivalent. For example, if MathML is used to mark up an equation, then a person with a MathML capable browser can properly read the equation.

4.4 Lists

Checkpoints in this section: 3.6.

The HTML list elements DL, UL, and OL should only be used to create lists, not for formatting effects such as indentation.

Ordered lists help non-visual users navigate. Non-visual users often "get lost" in lists, especially those with several layers of embedding and those that do not indicate the specific level of indentation for each item. Content developers are encouraged to use UL for unordered lists and OL for ordered lists (i.e., use markup appropriately). However, until user agents provide a means to identify list context clearly (e.g., by supporting the ':before' pseudo-element in CSS2), content developers should consider including contextual clues in their lists.

Please note that even for numbered lists, compound numbers are more informative than simple numbers. Thus, a list numbered like this:

is more informative than a list numbered like this:

[CSS1] and [CSS2] even more so provide ways to control list numbering styles. Users may apply list numbering styles even to unordered lists through user style sheets.

Non-visual users may have difficulties knowing where a list itself begins and ends and where each list item starts. Furthermore, if a list entry wraps to the next line on the screen, it may appear to be two separate items in the list. This may pose a problem for legacy screen readers.


The following CSS2 style sheet shows how to provide compound numbers for nested lists created with either UL or OL elements. Items are numbered as "1", "1.1", "1.1.1", etc.

<STYLE type="text/css">
   UL, OL { counter-reset: item }
   LI { display: block }
   LI:before { content: counters(item, "."); counter-increment: item }

Until either CSS2 is widely supported by users agents or user agents allow users to control rendering of lists through other means, authors should consider providing contextual clues in nested lists. The following CSS1 mechanism shows how to hide the end of a list when style sheets are turned on and to reveal it when style sheets are turned off, when user style sheets override the hiding mechanism, or when style sheets are not supported:

   <TITLE>Contextual clues in nested lists</TITLE>
   <STYLE type="text/css">
      .endoflist { display: none }
       <LI>Poster paper 
          <SPAN class="endoflist">(End of Paper)</SPAN>
       <LI>Blue writing pens
       <LI>whiteboard pens 
          <SPAN class="endoflist">(End of Pens)</SPAN>
       <LI>paper clips
       <LI>Big lengths of rope. 
          <SPAN class="endoflist">(End of Fasteners)</SPAN>

End example.

4.4.1 Use style sheets to change list bullets

To change the "bullet" style of unordered list items created with the LI element, use style sheets. This way, if images are not loaded, the browser will draw a default bullet.


<TITLE>Using style sheets to change bullets</TITLE>
<STYLE type="text/css">
   UL { list-style: url(star.gif) }

End example.

Avoid using images as bullets in definition lists created with DL, DT, and DD. However, if this method is used, be sure to provide a text equivalent for the images.

Deprecated example.

<TITLE>Deprecated example using image in DL lists</TITLE>
   <DD><IMG src="star.gif" alt="Item">Audrey
   <DD><IMG src="star.gif" alt="Item">Laurie
   <DD><IMG src="star.gif" alt="Item">Alice

Content developers should avoid list styles where bullets provide additional (visual) information. However, if this is done, be sure to provide a text equivalent describing meaning of the bullet:

Deprecated example.

<DD><IMG src="red.gif" alt="New:">Roth IRA</DD>
<DD><IMG src="yellow.gif" alt="Old:">401(k)</DD>

Here is a better way to change list bullet styles (using style sheets). To further ensure that users understand differences between list items indicated visually, content developers should provide a label before or after the list item phrase:


<TITLE>Bullet styles example</TITLE>
<STYLE type="text/css">
   .newtxt { font-weight: bold;
             color: red;
             background-color: yellow }
   .newbullet { list-style : url(yellow.gif) }
   <LI class="newbullet">Roth IRA <SPAN class="newtext">New</SPAN></LI>
   <LI> 401(k)</LI>

End example.

4.5 Tables

This section discusses the accessibility of tables and elements that one can put in a TABLE element.

Checkpoints in this section: 5.5, 5.1, 5.2, 5.6, and 5.4.

Content developers may make tables more accessible in a number of ways:

Most of the above elements and attributes are only available in HTML 4.0.

This markup will allow accessible browsers and other user agents to restructure or navigate tables in a non-visual manner.

For information about table headers, refer to the table header algorithm and discussion in the HTML 4.0 Recommendation ([HTML40], section 11.4.3).

The following example shows how to associate data cells (created with TD) with their corresponding headers by means of the "headers" attribute. The "headers" attribute specifies a list of header cells (row and column labels) associated with the current data cell. This requires each header cell to have an "id" attribute.

   <TABLE border="1" 
          summary="This table charts the number of
                   cups of coffee consumed by each senator,  
                   the type of coffee (decaf or regular),
                   and whether taken with sugar.">
     <CAPTION>Cups of coffee consumed by each senator</CAPTION>
         <TH id="header1">Name</TH>
         <TH id="header2">Cups</TH>     
         <TH id="header3" abbr="Type">Type of  Coffee</TH>   
         <TH id="header4">Sugar?</TH>
         <TD headers="header1">T. Sexton</TD>  
         <TD headers="header2">10</TD>
         <TD headers="header3">Espresso</TD>
         <TD headers="header4">No</TD>  
         <TD headers="header1">J. Dinnen</TD> 
         <TD headers="header2">5</TD>
         <TD headers="header3">Decaf</TD>
        <TD headers="header4">Yes</TD>

End example.

A speech synthesizer might render this tables as follows:

  Caption: Cups of coffee consumed by each senator
  Summary: This table charts the number of cups of coffee
           consumed by each senator, the type of coffee
          (decaf or regular), and whether taken with sugar.
  Name: T. Sexton, Cups: 10, Type: Espresso, Sugar: No
  Name: J. Dinnen, Cups: 5, Type: Decaf, Sugar: Yes

A visual user agent might render this table as follows:

Illustration of coffee table rendering [D]

The next example associates the same header (TH) and data (TD ) cells as before, but this time uses the "scope" attribute rather than "headers." "Scope" must have one of the following values: row, col, rowgroup or colgroup. Scope specifies the set of data cells to be associated with the current header cell. This method is particularly useful for simple tables. It should be noted that the spoken rendering of this table would be identical to that of the previous example. A choice between the "headers" and "scope" attributes is dependent on the complexity of the table. It does not affect the output so long as the relationships between header and data cells are made clear in the markup.


   <TABLE border="1" 
          summary="This table charts ...">  
      <CAPTION>Cups of coffee consumed by each senator</CAPTION>
           <TH scope="col">Name</TH>
           <TH scope="col">Cups</TH>
           <TH scope="col" abbr="Type">Type of Coffee</TH>  
           <TH scope="col">Sugar?</TH>
           <TD>T. Sexton</TD>  <TD>10</TD>
           <TD>Espresso</TD>   <TD>No</TD>
           <TD>J. Dinnen</TD>  <TD>5</TD>
           <TD>Decaf</TD>       <TD>Yes</TD>

End example.

The following example shows how to create categories within a table using the "axis" attribute.


   <TABLE border="1">
     <CAPTION>Travel Expense Report</CAPTION>
          <TH id="header2" axis="expenses">Meals
          <TH id="header3" axis="expenses">Hotels
          <TH id="header4" axis="expenses">Transport
          <TH id="header6" axis="location">San Jose
          <TH> <TH> <TH> <TD> 
         <TD id="header7" axis="date">25-Aug-97
         <TD headers="header6 header7 header2">37.74
         <TD headers="header6 header7 header3">112.00
         <TD headers="header6 header7 header4">45.00
         <TD id="header8" axis="date">26-Aug-97
         <TD headers="header6 header8 header2">27.28
         <TD headers="header6 header8 header3">112.00
         <TD headers="header6 header8 header4">45.00 
         <TH id="header10" axis="location">Seattle
         <TH> <TH> <TH> <TD>
         <TD id="header11" axis="date">27-Aug-97
         <TD headers="header10 header11 header2">96.25
         <TD headers="header10 header11 header3">109.00
         <TD headers="header10 header11 header4">36.00
         <TD id="header12" axis="date">28-Aug-97
         <TD headers="header10 header12 header2">35.00
         <TD headers="header10 header12 header3">109.00
         <TD headers="header10 header12 header4">36.00 

End example.

This table lists travel expenses at two locations: San Jose and Seattle, by date, and category (meals, hotels, and transport). The following image shows how a visual user agent might render it.

Travel Expense Report table as rendered by a visual user agent. [D]

4.5.1 Avoid tables for layout

Checkpoints in this section: 5.3.

Authors should use style sheets for layout and positioning. However, when it is necessary to use a table for layout, the table must be accessible:

4.5.2 Wrapped text in tables

Checkpoints in this section: 10.3.

Tables were originally designed to create presentations of data. Table markup is structural markup in that it defines the relationships between headers and cells. Clever Web developers found that they could control the layout of a page by using tables.

This misuse of tables is a source of problems for screen readers that do not interpret the source HTML or browsers that do not allow navigation of individual table cells. Screen readers will read across the page, reading sentences on the same row from different columns as one sentence.

For example, if a table is rendered like this on the screen:

There is a 30% chance of               Classes at the University of Wisconsin 
rain showers this morning, but they    will resume on September 3rd. 
should stop before the weekend.

This might be read by a screen reader as:

There is a 30% chance of Classes at the University of Wisconsin
rain showers this morning, but they will resume on September 3rd. 
should stop before the weekend.

Screen readers that read the source HTML will recognize the structure of each cell, but for older screen readers, content developers should minimize the risk of word wrapping by limiting the amount of text in each cell. Also, the longest chunks of text should all be in the last column (rightmost for left-to-right tables). This way, if they wrap, they will still be read coherently. Note that is a problem for all tables, even those used correctly to mark up data. This issue is being resolved by tools being created by the WAI Evaluation and Repair Working Group ([WAI-ER]).

Until user agents and screen readers are able to handle text presented side-by-side, all tables that lay out text in parallel, word-wrapped columns require a linear text alternative (on the current page or some other).

Content developers should test tables for wrapping with a browser window dimension of "640x480".

Since table markup is structural, and we suggest separating structure from presentation, we recommend using style sheets to create layout, alignment, and presentation effects. Thus, the two columns in the above example could have been created using style sheets. Please refer to the section on style sheets for more information.

Quicktest! To get a better understanding of how a screen reader would read a table, run a piece of paper down the page and read your table line by line.

4.5.3 Backward compatibility issues for tables

Rows of a TFOOT element will appear before the BODY of the document in an HTML3.2 browser.

4.6 Links

Checkpoints in this section: 13.1, and 13.6.

Users who are blind often jump from link to link when skimming a page or looking for information. When they do this, only the text of the link (the "link text") is read.

"Auditory users," people who are blind, have difficulty seeing, or who are using devices with small or no displays are unable to scan the page quickly with their eyes. To get an overview of a page or to quickly find a link, these users will often tab from one link to the next or review a list of available links on a page. When links are not descriptive enough, do not make sense when read out of context, or are not unique, these users must stop to read the text surrounding each link to identify it.

Avoid general link text, such as "click here." Not only is this phrase device-dependent (mouse-based) it says nothing about what is to be found if the link if followed. Instead of "click here", link text should indicate the nature of the link target, as in "more information about sea lions" or "text-only version of this page". Note that for the latter case (and other format- or language-specific documents), content developers are encouraged to use content negotiation instead, so that users who prefer text versions will have them served automatically.

In addition to clear link text, content developers may specify a value of the "title" attribute that clearly and accurately describes the target of the link.

If more than one link on a page shares the same link text, all those links should point to the same resource. Such consistency will help page design as well as accessibility. If two or more links refer to different targets but share the same link text, HTML authors should distinguish the links by specifying a different value for the "title" attribute of each A element.

However, there are times when the link text is the same, but the links do not have the same destination. For example, if a series of documents is provided in several formats, you do not need to state the name of the document as well as the format in every link. Instead include the name in the first link, then only use the format type in the following links. When read in succession, the user will hopefully be able to figure out the context due to the link text. Use "title" as discussed above.


  <A href="my-doc.html">My document is available in HTML</A>,
  <A href="my-doc.pdf" title="My document in PDF">PDF</A>,
  <A href="my-doc.txt" title="My document in text">plain text</A>

End example.

When an image is used as the content of a link, specify a text equivalent for the image.


  <A href="routes.html">
     <IMG src="topo.html" 
          alt="Current routes at Boulders Climbing Gym">

End example.

4.6.1 Grouping and bypassing links

When links are grouped into logical sets, such as in a navigation bar (a set of links that appears on every page in a site) they may be dealt with as a unit rather than as several pieces. Navigation bars are usually the first thing someone encounters on a page. For speech users, this means taking the time to read through a number of links on every page before reaching the unique content of a page. Therefore, grouping links will allow a user with a user agent that can navigate by elements, to jump over the group. This is similar to how people with vision skip reading the links when they see the same set on each page. Since this type of mechanism is not available today, providing a link that skips over the links, or using a tabindex at a link just before the content begins are strategies that work today. In the future, by grouping links, user agents will be able to deal with them as a group.

In HTML, use the DIV, SPAN, P, or FRAME elements to group links then identify the group with the "id" or "class" attributes. The following example uses P to group the links, "class" to identify it as a navigation bar, "tabindex" on an anchor following the group, and a link at the beginning of the group that links to the anchor after the group (since not all user agents support tabindex).


   <TITLE>How to use our site</TITLE>
     <P class="nav">    
       <A href="#how">[Bypass navigation bar</A> 
       <A href="home.html">[Home]</A>
       <A href="search.html">[Search]</A>
       <A href="new.html">[New and highlighted]</A>
       <A href="sitemap.html">[Site map]</A>     
     <H1><A name="how" tabindex=1>How to use our site</A></H1>
   <!-- content of page -->     

End example.

4.6.2 Keyboard access

In the following example, if the accesskey "C" is activated,"doc.html" is retrieved by the browser:


This example uses "accesskey":

   <A accesskey="C" href="doc.html" hreflang="en"
      title="XYZ company home page">
         XYZ company home page</A>

End example.

4.7 Images and image maps

Images include those that carry out simple animations (e.g., a "gif" image).

4.7.1 Text equivalents for images

Checkpoints in this section: 1.1.

When using IMG, specify a short text equivalent with the "alt" attribute. Note. The value of this attribute is referred to as "alt-text".


   <IMG src="magnifyingglass.gif" alt="Search">     

End example.

When using OBJECT, specify a text equivalent in the body of the OBJECT element:


   <OBJECT data="magnifyingglass.gif" type="image/gif">

End example.

When a short text equivalent does not suffice to adequately convey the function or role of an image, provide additional information in a file designated by the "longdesc" attribute:


   <IMG src="97sales.gif" alt="Sales for 1997" 

In sales97.html:

A chart showing how sales in 1997 progressed. The chart
is a bar-chart showing percentage increases in sales
by month. Sales in January were up 10% from December 1996,
sales in February dropped 3%, ..

End example.

For browsers that don't support "longdesc", provide a description link as well next to the graphic:


   <IMG src="97sales.gif" alt="Sales for 1997" longdesc="sales.html">
   <A href="sales.html" title="Description of 1997 sales figures">[D]</A>

End example.

Note. In the near future, a proxy ought to be able to translate a "longdesc" into a d-link.

When using OBJECT, provide a text equivalent in the content of the element:


   <OBJECT data="97sales.gif" type="image/gif">
          Sales in 1997 were down subsequent to our
          anticipated purchase ...

End example.

Or, provide a link to additional information from within the body of the element:


   <OBJECT data="97sales.gif" type="image/gif">
          Chart of our Sales in 1997.
          A <A href="desc.html">textual description</A> is available. 

End example.

4.7.2 Invisible d-links

An invisible d-link is a small (1 pixel) or transparent image whose "alt" attribute value is "D-link" or "D" and is part of the content of an A element. Like other d-links, it refers to a description of the associated image. Invisible d-links provide a (temporary) solution for designers who avoid d-links because a "D" next to a graphic disrupts the visual presentation. This practice has been deprecated in favor of using the "longdesc" attribute.

4.7.3 Ascii art

Checkpoints in this section: 1.5, and 13.10.

Avoid ascii art (character illustrations) and use real images instead since it is easier to supply a text equivalent for images. The priority of this checkpoint depends on the importance of the information (e.g., an important chart).

However, if ascii art must be used provide a link to jump over the ASCII art, as follows.


<a href="#post-art">skip over ASCII art</a>
<!-- ASCII art goes here -->
<a name="post-art">caption for ASCII art</a>

End example.

ASCII art may also be marked up as follows:


<OBJECT data="cow.txt" type="text/x-ascii-art" title="A WAI cow in ASCII art">
 / | WAI ||
*  ||----||

End example.

Another option is to use an ABBR element with "title".


<P><ABBR title="smiley in ascii art">:-)</ABBR>

End example.

If the ASCII art is complex, ensure that the text equivalent adequately describes it.

Another way to replace ascii art is to use human language substitutes. For example, <wink> might substitute for the emoticon <SPAN title="wink smiley">;-)</SPAN>, the word"therefore" could replace arrows consisting of dashes and greater than signs (e.g., -->), and the word "great" for the uncommon abbreviation "gr8".

4.7.4 Mathematical equations in images

4.7.5 Image maps

An image map is an image that has "active regions". When the user selects one of the regions, some action takes place -- a link may be followed, information sent to a server, etc. To make an image map accessible, content developers must ensure that each action associated with a visual region may be activated without a pointing device.

Image maps are created with the MAP element. HTML allows two types of image maps: client-side (the user's browser processes a URI) and server-side (the server processes click coordinates). For all image maps, content developers must supply a text equivalent.

Content developers should create client-side image maps (with "usemap") rather than server-side image maps (with "ismap") because server-side image maps require a specific input device. If server-side image maps must be used (e.g., because the geometry of a region cannot be represented with values of theshape attribute), authors must provide the same functionality or information in an alternative accessible format. One way to achieve this is to provide a textual link for each active region so that each link is navigable with the keyboard. If you must use a server-side image map, please consult the section on server-side image maps

4.7.6 Client-side image maps

Checkpoints in this section: 9.1, 1.2, and 10.5.

Provide text equivalents for image maps since they convey visual information.

If AREA is used to create the map, use the "alt" attribute:


   <IMG src="welcome.gif" alt="Image map of areas in the library"
   <MAP name="map1">
     <AREA shape="rect" coords="0,0,30,30"
           href="reference.html" alt="Reference">
     <AREA shape="rect" coords="34,34,100,100"
           href="media.html" alt="Audio visual lab">

End example.

The following example illustrates the same idea, but uses OBJECT instead of IMG to insert the image to provide more information about the image:


   <OBJECT data="welcome.gif" type="image/gif" usemap="#map1">
       There are several areas in the library including
       the <A href="reference.html">Reference</A> section and the
       <A href="media.html">Audio Visual Lab</A>.
   <MAP name="map1">
     <AREA shape="rect" coords="0,0,30,30"
           href="reference.html" alt="Reference">
     <AREA shape="rect" coords="34,34,100,100"
           href="media.html" alt="Audio visual lab">

End example.

In addition to providing a text equivalent, provide redundant textual links. If the A element is used instead of AREA, the content developer may describe the active regions and provide redundant links at the same time:


   <OBJECT data="navbar1.gif" type="image/gif" usemap="#map1">
   <MAP name="map1">
     <P>Navigate the site.
     <A href="guide.html" shape="rect"
        coords="0,0,118,28">[Access Guide]</A>
     <A href="shortcut.html" shape="rect"
     <A href="search.html" shape="circle"
     <A href="top10.html" shape="poly"
        coords="276,0,373,28,50,50">[Top Ten]</A>

End example.

Note that in the previous example the MAP element is the content of the OBJECT element so that the alternative links will only be displayed if the image map (navbar1.gif) is not.

Note also that links have been separated by brackets ([]). This is to prevent older screen readers from reading several adjacent links as a single link as well as helps sighted users distinguish between links visually.

Content developers should make sure they include printable characters (such as brackets or a vertical bar (|)) surrounded by spaces between adjacent links.

4.7.7 Server-side image maps

Checkpoints in this section: 3.8.

When a server-side image map must be used, content developers should provide an alternative list of image map choices. There are three techniques:

Server-side and client-side image maps may be used as submit buttons in Forms. For more information, refer to the section Graphical buttons.

4.8 Applets and other programmatic objects

While applets may be included in a document with either the APPLET or OBJECT element, OBJECT is the preferred method.

4.8.1 Text equivalents for applets and programmatic objects

If OBJECT is used, provide a text equivalent in the content of the element:


  <OBJECT classid="java:Press.class" width="500" height="500">
        As temperature increases, the molecules in the balloon...

End example.

A more complex example takes advantage of the fact the OBJECT elements may be embedded to provide for alternative representations of information:


  <OBJECT classid="java:Press.class" width="500" height="500">          
     <OBJECT data="Pressure.mpeg" type="video/mpeg">
        <OBJECT data="Pressure.gif" type="image/gif">
           As temperature increases, the molecules in the balloon...

End example.

If APPLET is used, provide a text equivalent with the "alt" attribute and in the content in the APPLET element. This enables the content to transform gracefully for those user agents that only support one of the two mechanisms ("alt" or content).

Deprecated example.

   <APPLET code="Press.class" width="500" height="500"
           alt="Java applet: how temperature affects pressure">
         As temperature increases, the molecules in the balloon...

4.8.2 Directly accessible applets

Checkpoints in this section: 8.1

If an applet (created with either OBJECT or APPLET) requires user interaction (e.g., the ability to manipulate a physics experiment) that cannot be duplicated in an alternative format, make the applet directly accessible.

For more information about accessible applets, please refer to [JAVAACCESS] and [IBMJAVA].

4.8.3 Audio and Video produced by dynamic objects

Checkpoints in this section: 8.1 and 1.4.

  1. Provide a text equivalent as for an image.

4.9 Audio and video

Audio and video should be accompanied by text transcripts, textual equivalents of auditory or visual events. When these transcripts are presented synchronously with a video presentation they are called "captions" and are used by people who cannot hear the audio track of the video material. Full audio transcripts include spoken dialogue as well as any other significant sounds including on-screen and off-screen sounds, music, laughter, applause, etc. The following two examples show captions, a text transcript, and auditory descriptions.


Captions for a scene from "E.T." The phone rings three times, then is answered.

[phone rings]




End example.


Here's an example of a transcript of a clip from "The Lion King" (available at [DVS]). Note that the Describer is providing the auditory description of the video track and that the description has been integrated into the transcript.

Simba: Yeah!

Describer: Simba races outside, followed by his parents. Sarabi smiles and nudges Simba gently toward his father. The two sit side-by-side, watching the golden sunrise.

Mufasa: Look Simba, everything the light touches is our kingdom.

Simba: Wow.

End example.

4.9.1 Audio information

Some media formats (e.g., QuickTime 3.0 and SMIL) allow captions and video descriptions to be added to the multimedia clip. SAMI allows captions to be added.

Until the format you are using supports alternative tracks, two versions of the movie could be made available, one with captions and descriptive video, and one without. Some technologies, such as SMIL and SAMI, allow separate audio/visual files to be combined with text files via a synchronization file to create captioned audio and movies.

Some technologies also allow the user to choose from multiple sets of captions to match their reading skills. For more information see the SMIL 1.0 ([SMIL]) specification.

Equivalents for sounds can be provided in the form of a text phrase on the page that links to a text transcript or description of the sound file. The link to the transcript should appear in a highly visible location such as at the top of the page. However, if a script is automatically loading a sound, it should also be able to automatically load a visual indication that the sound is currently being played and provide a description or transcript of the sound.

Note. Some controversy surrounds this technique because the browser should load the visual form of the information instead of the auditory form if the user preferences are set to do so. However, strategies must also work with today's browsers.

For more information, please refer to [NCAM].

4.9.2 Visual information and motion

Checkpoints in this section: 1.3, and 7.3.

Video descriptions are used primarily by people who are blind to follow the action and other non-auditory information in video material. The description provides narration of the key visual elements without interfering with the audio or dialogue of a movie. Key visual elements include actions, settings, body language, graphics, and displayed text.

For movies, provide auditory descriptions that are synchronized with the original audio. Refer to the section on audio information for more information about multimedia formats.

Text transcripts, in conjunction with the full audio transcript described above, allow access by people with both visual and hearing disabilities. This also provides everyone with the ability to index and search for information contained in audio/visual materials.

However, if necessary to include an applet that involves motion or updates, content developers should provide a mechanism for freezing this motion (for an example, refer to [TRACE]).

When necessary, a text equivalent should be provided for visual information to enable understanding of the page. For example, a looping animation that shows cloud cover and precipitation for the state of Wisconsin is included as part of a weather status report. Since the animation is supplementing the rest of the weather report (that is presented in natural language - text), a less verbose description of the animation is necessary. However, if the animation appears in a pedagogical setting where students are learning about cloud formations in relation to land mass, then the animation ought to be described for those who can not view the animation but who also want to learn the lesson.

See also the section on text style for controlling blinking.

4.9.3 Embedding multimedia objects

Other objects, such as those requiring a plug-in, should also use the OBJECT element. However, for backward compatibility with Netscape browsers, use the proprietary EMBED element within the OBJECT element as follows:


  <OBJECT classid="clsid:A12BCD3F-GH4I-56JK-xyz"
  codebase="http://site.com/content.cab" width=100 height=80> 
  <PARAM name="Movie" value="moviename.swf"> 
      <EMBED src="moviename.swf" width=100 height=80 

          <IMG alt="Still from Movie"
                  src="moviename.gif" width=100 height=80> 


End example.

For more information refer to [MACROMEDIA].

4.10 Frames

For visually enabled users, frames may organize a page into different zones. For non-visual users, relationships between the content in frames (e.g., one frame has a table of contents, another the contents themselves) must be conveyed through other means.

Frames as implemented today (with the FRAMESET, FRAME, and IFRAME elements) are problematic for several reasons:

In the following sections, we discuss how to make frames more accessible. We also provide an alternative to frames that uses HTML 4.0 and CSS and addresses many of the limitations of today's frame implementations.

4.10.1 Title frames for easy orientation

Checkpoints in this section: 12.1.


Use the "title" attribute to name frames.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
<TITLE>A simple frameset document</TITLE>
<FRAMESET cols="10%, 90%"
          title="Our library of electronic documents">  
    <FRAME src="nav.html" title="Navigation bar">  
    <FRAME src="doc.html" title="Documents">
       <A href="lib.html" title="Library link">   
             Select to go to the electronic library</A>  

End example.

4.10.2 Text equivalents for frames

Checkpoints in this section: 12.2.


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
    <TITLE>Today's news</TITLE>

  <FRAMESET COLS="10%,*,10%">

  <FRAMESET ROWS="20%,*">
    <FRAME SRC="promo.html" NAME="promo" title="promotions">
    <FRAME SRC="sitenavbar.html" NAME="navbar" 
       title="Sitewide navigation bar" longdesc="frameset-desc.html#navbar">

  <FRAME SRC="story.html" NAME="story" title="Selected story - main content" 

  <FRAMESET ROWS="*,20%">
    <FRAME SRC="headlines.html" NAME="index" title="Index of other 
      national headlines" longdesc="frameset-desc.html#headlines">
    <FRAME SRC="ad.html" NAME="adspace" title="Advertising">

    <p><a href="noframes.html">No frames version</a></p>
    <p><a href="frameset-desc.html">Descriptions of frames.</a></p>


frameset-desc.html might say something like:

#Navbar - this frame provides links to the major 
          sections of the site:  World News, National News,
          Local News, Technological News,
          and Entertainment News.

#Story  - this frame displays the currently selected story.

#Index  - this frame provides links to the day's 
          headline stories within this section.  

End example.

Note that if the a frame's contents change, the text equivalent will no longer apply. Also, links to a frame's longdesc ("d-links") ought to be provided with other alternative contents in the NOFRAMES element of a FRAMESET.

4.10.3 Ensure documents are readable without frames


In this example, if the user reads "top.html":

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
<TITLE>This is top.html</TITLE>
<FRAMESET cols="50%, 50%" title="Our big document">
    <FRAME src="main.html" title="Where the content is displayed">
    <FRAME src="table_of_contents.html" title="Table of Contents">
        <A href="table_of_contents.html">Table of Contents.</A>
     <!-- other navigational links that are available in main.html
          are available here also. -->

and the user agent is not displaying frames, the user will have access (via a link) to a non-frames version of the same information.

End example.

4.10.4 Always make the source of a frame an HTML document

Checkpoints in this section: 6.2.

Content developers must provide text equivalents of frames so that their contents and the relationships between frames make sense. Note that as the contents of a frame change, so must change any description. This is not possible if an IMG is inserted directly into a frame, as in this deprecated example:

Deprecated example.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
<TITLE>A bad frameset document</TITLE>
<FRAMESET cols="100%" title="Static frameset">
   <FRAME name="badframe"
          src="apples.gif" title="Apples">

Note that if, for example, a link causes a new image to be inserted into the frame:

  <P>Visit a beautiful grove of 
  <A target="badframe" href="oranges.gif" title="Oranges">oranges</A>

the initial title of the frame ("Apples") will no longer match the current content of the frame ("Oranges").

To solve this problem, content developers should always make the source ("src") of a frame an HTML file. Images may be inserted into the HTML file and their text alternatives will evolve correctly.


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN">
<TITLE>A correct frameset document</TITLE>
<FRAMESET cols="100%" title="Evolving frameset">
<FRAME name="goodframe" src="apples.html" title="Apples">
   <!-- In apples.html -->
   <P><IMG src="apples.gif" alt="Apples">

End example.

4.10.5 Avoid opening a new window as the target of a frame

Checkpoints in this section: 10.1.

Content developers should avoid specifying a new window as the target of a frame with target="_blank".

4.10.6 Alternatives to frames

One of the most common uses of frames is to split the user's browser window into two parts: a navigation window and a content window. As an alternative to frames, we encourage you to try the following:

  1. Create one document for the navigation mechanism (call it "nav.html"). A separate document means that the navigation mechanism may be shared by more than one document.
  2. In each document requiring the navigation mechanism, include it at the bottom of the document with the following (or similar) OBJECT markup:


    <OBJECT data="nav.html">
    Go to the <A href="nav.html">table of contents</A>

    Putting the navigation mechanism at the end of the document means that when style sheets are turned off, users have access to the document's important information first.

  3. Use style sheets to position the navigation mechanism where you want on the screen. For example, the following CSS rule floats the navigation bar to the left of the page and makes it take up 25% of the available horizontal space:
       OBJECT { float: left; width: 25% }

    The following CSS rule attaches the navigation mechanism to the bottom-left corner of the page of the page and keeps it there even if the user scrolls down the page:

       OBJECT { position: fixed; left: 0; bottom: 0 }

Note. Navigation mechanisms or other content may be inserted in a document by means of server-side includes.

4.11 Forms

This section discusses the accessibility of forms and form controls that one can put in a FORM element.

4.11.1 Make controls keyboard accessible

Checkpoints in this section: 9.4 and 9.5.

Refer to the section on keyboard access for more information.

4.11.2 Group form controls

Content developers should group information where natural and appropriate. When form controls can be grouped into logical units, use the FIELDSET element and label those units with the LEGEND element:


<FORM action="http://somesite.com/adduser" method="post">
   <LEGEND>Personal information</LEGEND>
   <LABEL for="firstname">First name: </LABEL>
   <INPUT type="text" id="firstname" tabindex="1">
   <LABEL for="lastname">Last name: </LABEL>
   <INPUT type="text" id="lastname" tabindex="2">
   ...more personal information...
   <LEGEND>Medical History</LEGEND>
   ...medical history information...

End example.

4.11.3 Label form controls explicitly

Checkpoints in this section: 12.4 and 10.2. An example of LABEL used with "for" in HTML 4.0 is given in the previous section.

4.11.4 Group menu options

Content developers should group information where natural and appropriate. For long lists of menu selections (which may be difficult to track), content developers should group SELECT items (defined by OPTION) into a hierarchy using the OPTGROUP element. Specifies a label for the group of options with the label attribute on OPTGROUP.


<FORM action="http://somesite.com/prog/someprog" method="post">
 <SELECT name="ComOS">
     <OPTGROUP label="PortMaster 3">
       <OPTION label="3.7.1" value="pm3_3.7.1">PortMaster 3 with ComOS 3.7.1
       <OPTION label="3.7" value="pm3_3.7">PortMaster 3 with ComOS 3.7
       <OPTION label="3.5" value="pm3_3.5">PortMaster 3 with ComOS 3.5
     <OPTGROUP label="PortMaster 2">
       <OPTION label="3.7" value="pm2_3.7">PortMaster 2 with ComOS 3.7
       <OPTION label="3.5" value="pm2_3.5">PortMaster 2 with ComOS 3.5
     <OPTGROUP label="IRX">
       <OPTION label="3.7R" value="IRX_3.7R">IRX with ComOS 3.7R
       <OPTION label="3.5R" value="IRX_3.5R">IRX with ComOS 3.5R

End example.

This example assigns "U" as the accesskey (via "accesskey"). Typing "U" gives focus to the label, which in turn gives focus to the input control, so that the user can input text.


   <FORM action="submit" method="post">
         <LABEL for="user" accesskey="U">name</LABEL>
         <INPUT type="text" id="user">

End example.

4.11.5 Keyboard access to forms

In the next example, we specify a tabbing order among elements (in order, "field2", "field1", "submit") with "tabindex":


   <FORM action="submit" method="post">
   <INPUT tabindex="2" type="text" name="field1">
   <INPUT tabindex="1" type="text" name="field2">
   <INPUT tabindex="3" type="submit" name="submit">

End example.

4.11.6 Graphical buttons

Using images to decorate buttons allows developers to make their forms unique and easier to understand. Using an image for a button (e.g., with the INPUT element or BUTTON) is not inherently inaccessible - assuming a text equivalent is provided for the image.

However, a graphical form submit button created with INPUT, type="image" creates a type of server-side image map. Whenever the button is clicked with a mouse, the x and y coordinates of the mouse click are sent to the server as part of the form request. An example is a bird button. When the user clicks on the tail, information about the tail is sent from the server and displayed in a text area following the bird button.

In the Image and Image Maps section we discuss why server-side images ought to be avoided, and suggest using client-side image maps instead. In HTML4, graphical buttons may now be client-side image maps. To preserve the functionality provided by the server, authors have the following options, as stated in the HTML4 Recommendations [HTML40] :

If the server takes different actions depending on the location clicked, users of non-graphical browsers will be disadvantaged.
For this reason, authors should consider alternate approaches:

4.11.7 Techniques for specific controls

Checkpoints in this section: 10.4 and 3.8.


Some legacy assistive technologies require initial text in form controls such as TEXTAREA in order to function properly.

<FORM action="http://somesite.com/prog/text-read" method="post">
     <TEXTAREA name=yourname rows="20" cols="80">
     Please enter your name here.
     <INPUT type="submit" value="Send"><INPUT type="reset">

End example.

Provide a text equivalent for images used as "submit" buttons:


<FORM action="http://somesite.com/prog/text-read" method="post">
<INPUT type="image" name=submit src="button.gif" alt="Submit">

End example.

Also refer to the section on keyboard access since this applies to form controls.

4.11.8 Backward compatibility issues for forms

The BUTTON element does not appear and <INPUT type="button"> will appear as a text input field in HTML3.2 browsers.

4.12 Scripts

This section discusses the accessibility of scripts included in a document via tha SCRIPT element.

4.12.1 Graceful transformation of scripts

Checkpoints in this section: 6.3.

Content developers must ensure that pages are accessible with scripts turned off or in browsers that don't support scripts.

Avoid creating content on the fly on the client. If a user is not running scripts, then no content will be displayed since their browser will not be able to generate it. However, this is different than displaying or hiding content by using a combination of style sheets and scripting - since the content exists it is just shown or hidden based on user action. If there is no script, then the content is always shown. This also does not rule out generating pages on the fly on the server-side then passing to the user agent.

Avoid creating links that use "javascript" as the URI. If a user is not using scripts, then they won't be able to link since the browser can't create the link content.

Example. This is a dead-end link for a user agent where scripts are not supported or not loaded.

    <A href="javascript:">...</A>

4.12.2 Device-independent event handlers

Checkpoints in this section: 9.3 and 6.4.

An event handler is a script that is invoked when a certain event occurs (e.g, the mouse moves, a key is pressed, the document is loaded, etc.). In HTML 4.0, event handlers are attached to elements via event handler attributes (the attributes beginning with "on", as in "onkeyup").

Some event handlers, when invoked, produce purely decorative effects such as highlighting an image or changing the color of an element's text. Other event handlers produce much more substantial effects, such as carrying out a calculation, providing important information to the user, or submitting a form. For event handlers that do more than just change the presentation of an element, content developers should do the following:

  1. Use application-level event triggers rather than user interaction-level triggers. In HTML 4.0, application-level event attributes are "onfocus", "onblur" (the opposite of "onfocus"), and "onselect". Note that these attributes are designed to be device-independent, but are implemented as keyboard specific events in current browsers.
  2. Otherwise, if you must use device-dependent attributes, provide redundant input mechanisms (i.e., specify two handlers for the same element):

    Note that there is no keyboard equivalent to double-clicking ("ondblclick") in HTML 4.0.

  3. Do not write event handlers that rely on mouse coordinates since this prevents device-independent input.

4.12.3 Alternative presentation of scripts

One way to accomplish this is with the NOSCRIPT element. The content of this element is rendered with scripts are not enabled.


<SCRIPT type="text/tcl">
 ...some Tcl script to show a billboard of sports scores...  
   <P>Results from yesterday's games:</P> 
      <DT>Bulls 91,  Sonics 80.
      <DD><A href="bullsonic.html">Bulls vs. Sonics game highlights</A> 
      ...more scores...  

End example.

5 CSS Techniques

Checkpoints in this section: 3.3.

The following sections list some techniques for using CSS to design accessible documents and some techniques for writing effective style sheets. In HTML, style sheets may be specified externally via the LINK element, in the document head via the STYLE element, or for a specific element via the style attribute.

CSS1 ([[CSS1]) and CSS2 ([[CSS2]) allow content developers to duplicate most HTML 4.0 presentation capabilities and offer more power with less cost. However, until most users have browsers that support style sheets, not every presentation idiom may be expressed satisfactorily with style sheets. We also provide examples of how to use HTML 4.0 features (e.g., tables, bitmap text) more accessibly when they must be used.

See also the section on text markup.

5.1 Guidelines for creating style sheets

Checkpoints in this section: 6.1 and 3.4.

Here are guidelines for creating style sheets that promote accessibility:

Some examples follow.


Use em to set font sizes, as in:

   H1 { font-size: 2em }
rather than:
   H1 { font-size: 12pt }

End example.


Use relative length units and percentages.

   BODY { margin-left: 15%; margin-right: 10%}

End example.


Only use absolute length units when the physical characteristics of the output medium are known.

   .businesscard { font-size: 8pt }

End example.


Always specify a fallback generic font:

   BODY { font-family: "Gill Sans", sans-serif }

End example.


Use numbers, not names, for colors:

   H1 {color: #808000}
   H1 {color: rgb(50%,50%,0%)}

End example.

5.2 Fonts

Instead of using deprecated presentation elements and attributes , use the many CSS properties to control font characteristics: 'font-family', 'font-size', 'font-size-adjust', 'font-stretch', 'font-style', 'font-variant', and 'font-weight'.

The following CSS2 properties can be used to control font information: 'font', 'font-family', 'font-size', 'font-size-adjust', 'font-stretch', 'font-style', 'font-variant', and 'font-weight'.

Use them instead of the following deprecated font elements and attributes in HTML: FONT, BASEFONT, "face", and "size".

If you must use HTML elements to control font information, use BIG and SMALL, which are not deprecated.


<STYLE type="text/css">
   P.important { font-weight: bold }
   P.less-important { font-weight: lighter; font-size: smaller }
   H2.subsection { font-family: Helvetica, sans-serif }

End example.

5.3 Text style

Checkpoints in this section: 7.2.

The following CSS2 properties can be used to style text:

5.3.1 Text instead of images

Content developers should use style sheets to style text rather than representing text in images. Using text instead of images means that the information will be available to a greater number of users (with speech synthesizers, braille displays, graphical displays, etc.). Using style sheets will also allow users to override author styles and change colors or fonts sizes more easily.

If it is necessary to use a bitmap to create a text effect (special font, transformation, shadows, etc.) the bitmap must be accessible (see the sections on text equivalents and alternative pages).


In this example, the inserted image shows the large red characters "Example", and is captured by the value of the "alt" attribute.

<P>This is an 
   <IMG src="BigRedExample.gif" alt="Example in big red characters"> 
   of what we mean.

End example.

5.4 Text formatting

The following CSS2 properties can be used to control the formatting and position of text:

The following example shows how to use style sheets to create a drop-cap effect.


<TITLE>Drop caps</TITLE>
<STYLE type="text/css">
      .dropcap { font-size : 120%; font-family : Helvetica } 
<P><SPAN class="dropcap">O</SPAN>nce upon a time...

Note. As of the writing of this document, the CSS pseudo-element ':first-letter', which allows content developers to refer to the first letter of a chunk of text, is not widely supported.

5.5 Colors

Checkpoints in this section: 2.1 and 2.2.

Use these CSS properties to specify colors:

Ensure that information is not conveyed through color alone. For example, when asking for input from users, do not write "Please select an item from those listed in green." Instead, ensure that information is available through other style effects (e.g., a font effect) and through context (e.g,. comprehensive text links).

For instance, in this document, examples are styled by default (through style sheets) as follows:

Quicktest! To test whether your document still works without colors, examine it with a monochrome monitor or browser colors turned off. Also, try setting up a color scheme in your browser that only uses black, white, and the four browser-safe greys and see how your page holds up.

Quicktest! To test whether color contrast is sufficient to be read by people with color deficiencies or by those with low resolution monitors, print pages on a black and white printer (with backgrounds and colors appearing in grayscale). Also try taking the printout and copying it for two or three generations to see how it degrades. This will show you where you need to add redundant cues (example: hyperlinks are usually underlined on Web pages), or whether the cues are two small or indistinct to hold up well.

For more information about colors and contrasts, refer to [LIGHTHOUSE].

5.6 Layout, positioning, layering, and alignment

Checkpoints in this section: ??

Layout, positioning, layering, and alignment should be done through style sheets (notably by using CSS floats and absolute positioning):

5.6.1 If you must use images as spacers

Provide text equivalents for all images, including invisible or transparent images.

If content developers cannot use style sheets and must use invisible or transparent images (e.g., with IMG) to lay out images on the page, they should specify alt="" for them.

Deprecated example.

In this example, an image is used to create a carefully defined space between words or graphics. Using only spaces for the value of "alt" prevents the words from running together when the image is not loaded:

   my poem requires a big space<IMG src="10pttab.gif" alt="&nbsp;&nbsp;&nbsp;">here

In this next example, an image is used to force a graphic to appear in a certain position:

   <IMG src="spacer.gif" alt="spacer">
   <IMG src="colorfulwheel.gif" alt="The wheel of fortune">

End example.

5.7 Rules and borders

Rules and borders may convey the notion of "separation" to visually enabled users but that meaning cannot be inferred out of a visual context.

Use these CSS properties to specify border styles:

Authors should use style sheets to create rules and borders.


In this example, the H1 element will have a top border that is 2px thick, red, and separated from the content by 1em:

   <TITLE>Redline with style sheets</TITLE>
   <STYLE type="text/css">
        H1 { padding-top: 1em; border-top: 2px red }
   <H1>Chapter 8 - Auditory and Tactile Displays</H1>

End example.

If a rule (e.g., the HR element) is used to indicate structure, be sure to indicate the structure in a non-visual way as well. (e.g., by using structural markup).


In this example, the DIV element is used to create a navigation bar, which includes a horizontal separator.

   <DIV class="navigation-bar">
      <A rel="Next" href="next.html">[Next page]</A>
      <A rel="Previous" href="previous.html">[Prevous page]</A>
      <A rel="First" href="first.html">[First page]</A>

End example.

6 XML Techniques

Under construction.

Checkpoint Map

This index lists each checkpoint and the sections in this document where it is discussed.

Guideline 1:

1.1 Provide a text equivalent for every non-text element (e.g., via "alt", "longdesc", or in element content). This includes: images, graphical representations of text (including symbols), image map regions, animations (e.g., animated GIFs), applets and programmatic objects, ascii art, frames, scripts, images used as list bullets, spacers, graphical buttons, sounds (played with or without user interaction), stand-alone audio files, synthesized speech, audio tracks of video, and video.
Refer to 3.2 Text equivalents and
4.7.1 Text equivalents for images
1.2 Provide redundant text links for each active region of an image map. [Priority 1 - if server-side image maps are used, Priority 2 - if client-side image maps are used. Redundant text links for client-side image maps are only required until user agents render text equivalents for the map links.]
Refer to 3.2 Text equivalents and
4.7.6 Client-side image maps
1.3 For each movie, provide an auditory description of the video track and synchronize it with the audio track.
Refer to 4.9.2 Visual information and motion
1.4 For any time-based presentation (e.g., a movie, animation, or multimedia presentation), synchronize equivalent alternatives (e.g., captions or video descriptions) with the presentation.
Refer to 4.8.3 Audio and Video produced by dynamic objects
1.5 Replace ASCII art with an image or explain it. [Priority 1 or Priority 2 depending on the importance of the information.]
Refer to 3.2 Text equivalents and
4.7.3 Ascii art

Guideline 2:

2.1 Ensure that all information conveyed with color is also available without color, for example from context or markup.
Refer to 5.5 Colors
2.2 Ensure that foreground and background color combinations provide sufficient contrast when viewed by someone having color deficits or when viewed on a black and white screen. [Priority 2 for images, Priority 3 for text].
Refer to 5.5 Colors

Guideline 3:

3.1 When an appropriate markup language exists, use markup rather than images to convey information.
Refer to 4.3.5 Text markup rather than images
3.2 Create documents that validate to published formal grammars.
Refer to 4.1 Document structure and metadata
3.3 Use style sheets to control layout and presentation.
Refer to 3.2 Text equivalents and
5 CSS Techniques
3.4 Use relative rather than absolute units in markup language attribute values and style sheet property values.
Refer to 5.1 Guidelines for creating style sheets
3.5 Use header elements to convey logical structure and use them according to specification.
Refer to 4.1.2 Section headers
3.6 Mark up lists and list items properly.
Refer to 4.4 Lists
3.7 Mark up quotations. Do not use quotation markup for formatting effects such as indentation.
Refer to 4.3.3 Quotations
3.8 Provide individual button controls in a form rather than simulating a set of buttons with an image map.
Refer to 3.2 Text equivalents and
4.7.7 Server-side image maps and
4.11.7 Techniques for specific controls

Guideline 4:

4.1 Clearly identify changes in the natural language of a document's text and any text equivalents (e.g., captions) of non-text content.
Refer to 4.2 Language information
4.2 Specify the expansion of abbreviations and acronyms. [Priority 2 for the first occurrence of the acronym or abbreviation in a given document, Priority 3 thereafter.]
Refer to 4.3.2 Acronyms and abbreviations
4.3 Identify the primary natural language of a document.
Refer to 4.2 Language information

Guideline 5:

5.1 For data tables, identify row and column headers.
Refer to 4.5 Tables
5.2 For data tables that have two or more logical levels of row or column headers, use markup to associate data cells and header cells.
Refer to 4.5 Tables
5.3 Avoid using tables for layout.
Refer to 4.5.1 Avoid tables for layout
5.4 If a table is used for layout, do not use any structural markup for the purpose of visual formatting.
Refer to 4.5 Tables
5.5 Provide summaries for tables.
Refer to 4.5 Tables
5.6 Provide abbreviations for header labels.
Refer to 4.5 Tables

Guideline 6:

6.1 Organize documents so they may be read without style sheets. For example, when an HTML document is rendered without associated style sheets, it must still be possible to read the document.
Refer to 5.1 Guidelines for creating style sheets
6.2 Ensure that descriptions and text equivalents for dynamic content are updated when the dynamic content changes.
Refer to 4.10.4 Always make the source of a frame an HTML document
6.3 Ensure that pages are usable when scripts, applets, or other programmatic objects are turned off or not supported. If this is not possible, provide equivalent mechanisms on an alternative accessible page.
Refer to 4.12.1 Graceful transformation of scripts
6.4 For scripts and applets, until user agents provide device-independent means to activate event handlers, ensure that event handlers are keyboard operable.
Refer to 4.12.2 Device-independent event handlers
6.5 Provide an alternative presentation or page when the primary content is dynamic (e.g., when frame contents change, when scripts cause changes, etc.).
Refer to 3.3 Alternative pages

Guideline 7:

7.1 Until user agents allow users to control it, avoid causing the screen to flicker.
Refer to 3.9 Other topics
7.2 Until user agents allow users to control it, avoid causing content to blink (i.e., change presentation at a regular rate, such as turning on and off).
Refer to 5.3 Text style
7.3 Until user agents allow users to freeze moving content, avoid movement in pages.
Refer to 4.9.2 Visual information and motion
7.4 Until user agents provide the ability to stop the refresh, do not create periodically auto-refreshing pages.
Refer to 3.8 Automatic page refresh
7.5 Until user agents provide the ability to stop auto-redirect, do not use markup to redirect pages automatically. Instead, configure the server to perform redirects.
Refer to 3.8 Automatic page refresh

Guideline 8:

8.1 Make programmatic elements such as scripts and applets directly accessible or compatible with assistive technologies [Priority 1 if functionality is important and not presented elsewhere, otherwise Priority 2.]
Refer to 4.8.2 Directly accessible applets and
4.8.3 Audio and Video produced by dynamic objects

Guideline 9:

9.1 Provide client-side image maps instead of server-side image maps except where the regions cannot be defined with an available geometric shape.
Refer to 4.7.6 Client-side image maps
9.2 Ensure that all elements that have their own interface are keyboard operable.
Refer to 3.4 Keyboard access
9.3 For scripts, specify logical event handlers rather than device-dependent event handlers.
Refer to 4.12.2 Device-independent event handlers
9.4 Create a logical tab order through links, form controls, and objects.
Refer to 4.11.1 Make controls keyboard accessible
9.5 Provide keyboard shortcuts to important links (including those in client-side image maps), form controls, and groups of form controls.
Refer to 4.11.1 Make controls keyboard accessible

Guideline 10:

10.1 Until user agents allow users to turn off spawned windows, do not cause pop-ups or other windows to appear and do not change the current window without informing the user.
Refer to 4.10.5 Avoid opening a new window as the target of a frame
10.2 For all form controls with implicitly associated labels, ensure that the label is properly positioned.
Refer to 4.11.3 Label form controls explicitly
10.3 Until user agents or assistive technologies render side-by-side text correctly, provide a linear text alternative (on the current page or some other) for all tables that lay out text in parallel, word-wrapped columns.
Refer to 4.5.2 Wrapped text in tables
10.4 Until user agents handle empty controls correctly, include default, place-holding characters in edit boxes and text areas.
Refer to 4.11.7 Techniques for specific controls
10.5 Until user agents or assistive technologies render adjacent links distinctly, include non-link, printable characters (surrounded by spaces) between adjacent links.
Refer to 4.7.6 Client-side image maps

Guideline 11:

11.1 Use W3C technologies and use the latest versions when they are supported.
Refer to 3.11 Browser Support
11.2 Avoid deprecated features of W3C technologies.
Refer to
11.3 Provide information so that users may receive documents according to their preferences (e.g., language, content type, etc.)
Refer to 3.7 Content negotiation
11.4 If, after best efforts, you cannot create an accessible page, provide a link to an alternative page that uses W3C technologies, is accessible, has equivalent information, and is updated as often as the inaccessible (original) page.
Refer to 3.3 Alternative pages

Guideline 12:

12.1 Title each frame to facilitate frame identification and navigation.
Refer to 3.2 Text equivalents and
4.10.1 Title frames for easy orientation
12.2 Describe the purpose of frames and how frames relate to each other if it is not obvious by frame titles alone.
Refer to 3.2 Text equivalents and
4.10.2 Text equivalents for frames
12.3 Divide large blocks of information into more manageable groups where natural and appropriate.
Refer to 3.6 Comprehension
12.4 Associate labels explicitly with their controls.
Refer to 4.11.3 Label form controls explicitly

Guideline 13:

13.1 Clearly identify the target of each link.
Refer to 4.6 Links
13.2 Provide metadata to add semantic information to pages and sites.
Refer to 3.5 Navigation
13.3 Provide information about the general layout of a site (e.g., a site map, or table of contents).
Refer to 3.5 Navigation
13.4 Use navigation mechanisms in a consistent manner.
Refer to 3.5 Navigation
13.5 Provide navigation bars to highlight and give access to the navigation mechanism.
Refer to 3.5 Navigation
13.6 Group related links, identify the group (for user agents), and, until user agents do so, provide a way to bypass the group.
Refer to 4.6 Links
13.7 Enable different types of searches for different skill levels and preferences.
Refer to 3.5 Navigation
13.8 Place distinguishing information at the beginning of headings, paragraphs, lists, etc.
Refer to 3.5 Navigation
13.9 Provide information about document collections (i.e., documents comprising multiple pages.).
Refer to 3.9 Other topics
13.10 Provide a means to skip over multi-line ASCII art.
Refer to 3.2 Text equivalents and
4.7.3 Ascii art

Guideline 14:

14.1 Use the clearest and simplest language appropriate for a site's content.
Refer to 3.6 Comprehension
14.2 Provide visual or auditory equivalents to text where they facilitate comprehension of the page.
Refer to 3.6 Comprehension
14.3 Create a style of presentation that is consistent across pages.
Refer to 3.5 Navigation

Index of HTML elements and attributes

Checkpoints in this section: 11.2.


Linear version of HTML 4.0 element index.

This index lists all elements in HTML 4.0. The first column of this table links to the definition of the element in the HTML 4.0 specification ([HTML40]). Elements that are deprecated in HTML 4.0 are followed by an asterisk (*). Elements that are obsolete in HTML 4.0 or don't exist in a W3C specification of HTML (2.0, 3.2, 4.0) do not appear in this table.

The second column indicates other W3C specifications for HTML that included each element. The third column indicates the element's role.

The last column lists the sections in the current document where the element is discussed. An entry of "N/A" means that the element is not discussed in this document.

Element name Defined in Role Techniques
A 2.0, 3.2 Structure 4.6 Links, 4.7.2 Invisible d-links, 4.7.6 Client-side image maps
ABBR   Structure 4.3.2 Acronyms and abbreviations, 4.7.3 Ascii art
ACRONYM   Structure 4.3.2 Acronyms and abbreviations, 4.3.3 Quotations
ADDRESS 2.0, 3.2 Metadata 4.1.1 Metadata
APPLET* 3.2 Replaced 4.8 Applets and other programmatic objects, 4.8.1 Text equivalents for applets and programmatic objects, 4.8.2 Directly accessible applets
AREA 3.2 Structure 4.7.6 Client-side image maps
B 2.0, 3.2 Presentation 4.3.1 Emphasis
BASE 2.0, 3.2 Processing N/A
BASEFONT* 3.2 Presentation 5.2 Fonts
BDO   Processing N/A
BIG 3.2 Presentation 5.2 Fonts
BLOCKQUOTE 2.0, 3.2 Structure 3.1 Structure vs. Presentation, 4.3.3 Quotations, 5.4 Text formatting
BODY 2.0, 3.2 Structure N/A
BR 2.0, 3.2 Presentation N/A
BUTTON   Structure 4.11.6 Graphical buttons
CAPTION 3.2 Structure 3.6 Comprehension, 4.5 Tables
CENTER* 3.2 Presentation 5.6 Layout, positioning, layering, and alignment
CITE 2.0, 3.2 Structure 4.3.4 Miscellaneous structural markup
CODE 2.0, 3.2 Structure 4.3.4 Miscellaneous structural markup
COL   Structure 4.5 Tables
COLGROUP   Structure 3.6 Comprehension, 4.5 Tables
DD 2.0, 3.2 Structure 4.4.1 Use style sheets to change list bullets
DEL   Metadata 4.3.4 Miscellaneous structural markup
DFN 3.2 Structure 4.3.4 Miscellaneous structural markup
DIR* 2.0, 3.2 Structure N/A
DIV 3.2 Structure 4.6.1 Grouping and bypassing links
DL 2.0, 3.2 Structure 3.6 Comprehension, 4.4 Lists, 4.4.1 Use style sheets to change list bullets
DT 2.0, 3.2 Structure 4.4.1 Use style sheets to change list bullets
EM 2.0, 3.2 Structure 4.3.1 Emphasis
FIELDSET   Structure 3.6 Comprehension, 4.11.2 Group form controls
FONT* 3.2 Presentation 5.2 Fonts
FORM 2.0, 3.2 Structure 4.11 Forms
FRAME   Replaced 4.6.1 Grouping and bypassing links, 4.10 Frames
FRAMESET   Presentation 4.10 Frames, 4.10.2 Text equivalents for frames
H1 2.0, 3.2 Structure 3.1 Structure vs. Presentation, 3.6 Comprehension, 4.1.2 Section headers, 5.7 Rules and borders
HEAD 2.0, 3.2 Structure N/A
HR 2.0, 3.2 Presentation 3.1 Structure vs. Presentation, 4.1.2 Section headers, 5.7 Rules and borders
HTML 2.0, 3.2 Structure N/A
I 2.0, 3.2 Presentation 4.3.1 Emphasis
IFRAME   Replaced 4.10 Frames
IMG 2.0, 3.2 Replaced 4.7.1 Text equivalents for images, 4.7.7 Server-side image maps, 5.6.1 If you must use images as spacers
INPUT 2.0, 3.2 Structure 4.11.6 Graphical buttons
INS   Metadata 4.3.4 Miscellaneous structural markup
ISINDEX* 2.0, 3.2 Structure N/A
KBD 2.0, 3.2 Structure 4.3.4 Miscellaneous structural markup
LABEL   Structure 4.11.3 Label form controls explicitly
LEGEND   Structure 3.6 Comprehension, 4.11.2 Group form controls
LI 2.0, 3.2 Structure 4.4.1 Use style sheets to change list bullets
LINK 2.0, 3.2 Metadata 3.3 Alternative pages, 3.5 Navigation, 3.9 Other topics, 4.1.1 Metadata, 5 CSS Techniques
MAP 3.2 Structure 4.7.5 Image maps
MENU* 2.0, 3.2 Structure N/A
META 2.0, 3.2 Metadata 3.8 Automatic page refresh, 4.1.1 Metadata
NOFRAMES   Alternative 4.10.2 Text equivalents for frames
NOSCRIPT   Alternative 4.12.3 Alternative presentation of scripts
OBJECT   Replaced 3.2.1 Overview of technologies, 4.7.1 Text equivalents for images, 4.7.6 Client-side image maps, 4.7.7 Server-side image maps, 4.8 Applets and other programmatic objects, 4.8.1 Text equivalents for applets and programmatic objects, 4.8.2 Directly accessible applets, 4.9.3 Embedding multimedia objects, 4.10.6 Alternatives to frames
OL 2.0, 3.2 Structure 3.6 Comprehension, 4.4 Lists
OPTGROUP   Structure 3.6 Comprehension, 4.11.4 Group menu options
OPTION 2.0, 3.2 Structure 4.11.4 Group menu options
P 2.0, 3.2 Structure 3.6 Comprehension, 4.6.1 Grouping and bypassing links
PARAM 3.2 Processing N/A
PRE 2.0, 3.2 Presentation 4.5 Tables
Q   Structure 4.3.3 Quotations
S*   Presentation N/A
SAMP 2.0, 3.2 Structure 4.3.4 Miscellaneous structural markup
SCRIPT 3.2 (DTD) Processing 4.12 Scripts
SELECT 2.0, 3.2 Structure 4.11.4 Group menu options
SMALL 3.2 Presentation 5.2 Fonts
SPAN   Structure 4.6.1 Grouping and bypassing links
STRIKE* 3.2 Presentation N/A
STRONG 2.0, 3.2 Structure 4.3.1 Emphasis
STYLE 3.2 (DTD) Processing 5 CSS Techniques
SUB 3.2 Presentation N/A
SUP 3.2 Presentation N/A
TABLE 3.2 Structure 4.5 Tables
TBODY   Structure 3.6 Comprehension, 4.5 Tables
TD 3.2 Structure 4.5 Tables
TEXTAREA 2.0, 3.2 Structure 4.11.7 Techniques for specific controls
TFOOT   Structure 3.6 Comprehension, 4.5 Tables
TH 3.2 Structure 4.5 Tables
THEAD   Structure 3.6 Comprehension, 4.5 Tables
TITLE 2.0, 3.2 Metadata 4.1.1 Metadata
TR 3.2 Structure N/A
TT 2.0, 3.2 Presentation N/A
U* 3.2 Presentation N/A
UL 2.0, 3.2 Structure 3.6 Comprehension, 4.4 Lists
VAR 2.0, 3.2 Structure 4.3.4 Miscellaneous structural markup


Linear version of HTML 4.0 attribute index.

This index lists some attributes in HTML 4.0 that affect accessibility and what elements they apply to. The first column of this table links to the definition of the attribute in the HTML 4.0 specification ([HTML40]). Attributes and elements that are deprecated in HTML 4.0 ([HTML40]) are followed by an asterisk (*). Attributes and elements that are obsolete in HTML 4.0 or don't exist in a W3C specification of HTML (2.0, 3.2, 4.0) do not appear in this table. Attributes that apply to most elements of HTML 4.0 are indicated as such; please consult the HTML 4.0 specification for the exact list of elements with this attribute.

The second column indicates other W3C specifications for HTML that included each attribute. The third column indicates the elements that take each attribute. The fourth column indicates the attribute's role.

The last column lists the sections in the current document where the attribute is discussed. An entry of "N/A" means that the attribute is not discussed in this document.

Attribute name Applies to elements Role Techniques
abbr TD, TH Alternative 4.5 Tables
accesskey A, AREA, BUTTON, INPUT, LABEL, LEGEND, TEXTAREA User Interface 4.6.2 Keyboard access, 4.11.4 Group menu options
alt APPLET, AREA, IMG, INPUT Alternative 3.2.1 Overview of technologies, 4.7.1 Text equivalents for images, 4.7.2 Invisible d-links, 4.7.6 Client-side image maps, 4.7.7 Server-side image maps, 4.8.1 Text equivalents for applets and programmatic objects, 5.6.1 If you must use images as spacers
axis TD, TH Structure 4.5 Tables
class Most elements Structure 4.6.1 Grouping and bypassing links
dir Most elements Processing N/A
for LABEL Structure 4.11.3 Label form controls explicitly
headers TD, TH Structure 4.5 Tables
hreflang A, LINK Metadata 3.7 Content negotiation
id Most elements Structure 4.6.1 Grouping and bypassing links
label OPTION Alternative 4.11.4 Group menu options
lang Most elements Metadata 4.2 Language information
longdesc IMG, FRAME, IFRAME Alternative 3.2.1 Overview of technologies, 4.7.1 Text equivalents for images
name FRAME Structure N/A
scope TD, TH Structure 4.5 Tables
style Most elements Processing 5 CSS Techniques
summary TABLE Alternative 4.5 Tables
tabindex A, AREA, BUTTON, INPUT, OBJECT, SELECT, TEXTAREA User Interface 4.6.1 Grouping and bypassing links, 4.11.5 Keyboard access to forms
title Most elements Metadata 4.1.1 Metadata, 4.3.2 Acronyms and abbreviations, 4.6 Links, 4.7.3 Ascii art
usemap IMG, INPUT, OBJECT Processing 4.7.5 Image maps

The following is the list of HTML 4.0 attributes not directly related to accessibility. Content developers should use style sheets instead of presentation attributes. For even handler attributes, please refer to the section on device-independent event handlers for more detail.

Other structural attributes:
start*, value*, rowspan, colspan, span
Other presentation attributes:
align*, valign*, clear*, nowrap*, char, charoff, hspace*, vspace*, cellpadding, cellspacing, compact*, face*, size*, background*, bgcolor*, color*, text*, link*, alink*, vlink*, border, noshade*, rules, size (deprecated according to element), marginheight, marginwidth, frame, frameborder, rows, cols
Other processing instruction attributes:
ismap, coords, shape
Other user interface attributes:
target, scrolling, noresize
Other metadata attributes:
type, cite, datetime
Event handler attributes:
onblur, onchange, onclick, ondblclick, onfocus, onkeydown, onkeypress, onkeyup, onload, onload, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup, onreset, onselect, onsubmit, onunload


Web Content Guidelines Working Group Co-Chairs:
Chuck Letourneau, Starling Access Services
Gregg Vanderheiden, Trace Research and Development
W3C Team contacts:
Judy Brewer and Daniel Dardailler
We wish to thank the following people who have contributed their time and valuable comments to shaping these guidelines:
Harvey Bingham, Kevin Carey, Chetz Colwell, Neal Ewers, Geoff Freed, Al Gilman, Larry Goldberg, Jon Gunderson, Eric Hansen, Phill Jenkins, Leonard Kasday, George Kerscher, Marja-Riitta Koivunen, Josh Krieger, Scott Luebking, William Loughborough, Murray Maloney, Charles McCathieNevile, MegaZone (Livingston Enterprises), Masafumi Nakane, Mark Novak, Charles Oppermann, Mike Paciello, David Pawson, Michael Pieper, Greg Rosmaita, Liam Quinn, Dave Raggett, T.V. Raman, Robert Savellis, Jutta Treviranus, Steve Tyler, Jaap van Lelieveld, and Jason White

The original draft of this document is based on "The Unified Web Site Accessibility Guidelines" ([UWSAG]) compiled by the Trace R & D Center at the University of Wisconsin. That document includes a list of additional contributors.

Reference specifications

For the latest version of any W3C specification please consult the list of W3C Technical Reports.

"CSS, level 1 Recommendation", B. Bos, H. Wium Lie, eds., 17 December 1996, revised 11 January 1999. The CSS1 Recommendation is available at: http://www.w3.org/TR/1999/REC-CSS1-19990111.
The latest version of CSS1 is available at: http://www.w3.org/TR/REC-CSS1.
"CSS, level 2 Recommendation", B. Bos, H. Wium Lie, C. Lilley, and I. Jacobs, eds., 12 May 1998. The CSS2 Recommendation is available at: http://www.w3.org/TR/1998/REC-CSS2-19980512.
The latest version of CSS2 is available at: http://www.w3.org/TR/REC-CSS2.
"Document Object Model (DOM) Level 1 Specification", V. Apparao, S. Byrne, M. Champion, S. Isaacs, I. Jacobs, A. Le Hors, G. Nicol, J. Robie, R. Sutor, C. Wilson, and L. Wood, eds., 1 October 1998. The DOM Level 1 Recommendation is available at: http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001.
The latest version of DOM Level 1 is available at: http://www.w3.org/TR/REC-DOM-Level-1
"HTML 4.0 Recommendation", D. Raggett, A. Le Hors, and I. Jacobs, eds., 17 December 1997, revised 24 April 1998. The HTML 4.0 Recommendation is available at: http://www.w3.org/TR/1998/REC-html40-19980424.
The latest version of HTML 4.0 is available at: http://www.w3.org/TR/REC-html40.
"HTML 3.2 Recommendation", D. Raggett, ed., 14 January 1997. The latest version of HTML 3.2 is available at: http://www.w3.org/TR/REC-html32.
"Mathematical Markup Language", P. Ion and R. Miner, eds., 7 April 1998. The MathML 1.0 Recommendation is available at: http://www.w3.org/TR/1998/REC-MathML-19980407.
The latest version of MathML 1.0 is available at: http://www.w3.org/TRREC-MathML.
"PNG (Portable Network Graphics) Specification", T. Boutell, ed., T. Lane, contributing ed., 1 October 1996. The latest version of PNG 1.0 is available at: http://www.w3.org/TR/REC-png.
"Resource Description Framework (RDF) Model and Syntax Specification", O. Lassila, R. Swick, eds., 22 February 1999. The RDF Recommendation is available at: http://www.w3.org/TR/1999/REC-rdf-syntax-19990222.
The latest version of RDF 1.0 is available at: http://www.w3.org/TR/REC-rdf-syntax
"Synchronized Multimedia Integration Language (SMIL) 1.0 Specification", P. Hoschka, ed., 15 June 1998. The SMIL 1.0 Recommendation is available at: http://www.w3.org/TR/1998/REC-smil-19980615
The latest version of SMIL 1.0 is available at: http://www.w3.org/TR/REC-smil
"Techniques for Web Content Accessibility Guidelines 1.0", W. Chisholm, G. Vanderheiden, I. Jacobs, eds. This document explains how to implement the checkpoints defined in "Web Content Accessibility Guidelines 1.0". The latest draft of the techniques is available at: http://www.w3.org/WAI/GL/WAI-WEBCONTENT-TECHS/
"Authoring Tool Accessibility Guidelines", J. Treviranus, J. Richards, I. Jacobs, C. McCathieNevile, eds. The latest Working Draft of these guidelines for designing accessible authoring tools is available at: http://www.w3.org/TR/WD-WAI-AUTOOLS/
"User Agent Accessibility Guidelines", J. Gunderson and I. Jacobs, eds. The latest Working Draft of these guidelines for designing accessible user agents is available at: http://www.w3.org/TR/WD-WAI-USERAGENT/
"The Unified Web Site Accessibility Guidelines", G. Vanderheiden, W. Chisholm, eds. The Unified Web Site Guidelines were compiled by the Trace R & D Center at the University of Wisconsin under funding from the National Institute on Disability and Rehabilitation Research (NIDRR),  U.S. Dept. of Education. This document is available at: http://www.tracecenter.org/docs/html_guidelines/version8.htm
"Extensible Markup Language (XML) 1.0.", T. Bray, J. Paoli, C.M. Sperberg-McQueen, eds., 10 February 1998. The XML 1.0 Recommendation is available at: http://www.w3.org/TR/1998/REC-xml-19980210.
The latest version of XML 1.0 is available at: http://www.w3.org/TR/REC-xml


Note. W3C cannot maintain stability for any of the following references outside of its control. These references are included for convenience.

DVS Descriptive Video Services.
Bobby is an automatic accessibility validation tool developed by Cast.
The W3C CSS Validation Service.
The W3C HTML Validation Service.
IBM Guidelines for Writing Accessible Applications Using 100% Pure Java are available from IBM Special Needs Systems.
Information about Java Accessibility and Usability is available from the Trace R&D Center.
The Lighthouse provides information about accessible colors and contrasts.
Lynx is a text-only browser.
Lynx-me is a Lynx emulator.
Lynx Viewer is a Lynx emulator.
Flash OBJECT and EMBED Tag Syntax from Macromedia.
The National Center for Accessible Media includes information about captioning and audio description on the Web.
The Trace Research & Development Center. Consult this site for a variet of information about accessibility, including a scrolling Java applet that may be frozen by the user.
The WAI Evaluation and Repair Working Group
Walsh, Norman. (1997). "A Guide to XML." In "XML: Principles, Tools, and Techniques." Dan Connolly, Ed. O'Reilly & Associates, 101 Morris St, Sebastopol, CA 95472. pp 97-107.
webreview.com style sheet browser compatibility charts.