This document provides guidelines to Web content developers (page authors and
site designers) for making
Web content accessible to people with
disabilities. While these guidelines have been developed to help
authors and authoring
tools create accessible Web content, following them will
also make Web content available to all users with different
user agents
(desktop browsers, voice browsers, mobile phones,
automobile-based PCs, etc.) or operating under various constraints
(noisy or noiseless surroundings, under- or over-illuminated rooms, in
a hands-free environment, etc.). Following these guidelines will also
help people find information on the Web more quickly. These guidelines
do not discourage content developers
from using images, video, etc., but rather
explain how to make multimedia pages more accessible to a wide
audience.
This document is part of a series of accessibility guidelines
published by the
W3C Web
Accessibility Initiative. The series also includes User Agent
Accessibility Guidelines ([WAI-USERAGENT]) and Authoring Tool
Accessibility Guidelines ([WAI-AUTOOLS]).
This is a W3C Working Draft for review by the WAI Page
Author Guidelines Working Group. It is published during
the last call period for this document, which ends
on March 19, 1999. This document incorporates many of
the changes sent by reviewers as a result of last call. It
is not entirely stable yet since not all of the suggestions
have been incorporated. The editors will continue to incorporate
comments and revise the document during and after last call.
This 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 WAI
GL Working Group.
This document has been produced as part of the W3C Web Accessibility Initiative, and
is intended as a draft of a Proposed Recommendation for creating
accessible Web content. The goal of the WAI Page Author 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.
The current document includes an appendix entitled "List of Checkpoints for the Web Content Accessibility Guidelines." This appendix
organizes all of the checkpoints defined in the current
document by topic and priority. The
checkpoints in the appendix link to their definitions in the current
document. The topics identified in the appendix include images,
multimedia, tables, frames, forms, and scripts.
A separate document, entitled "Techniques for Web Content Accessibility Guidelines," explains how to
implement these checkpoints. It discusses each checkpoint in more
detail and provides examples using HTML, Cascading Style Sheets (CSS),
and Synchronized Multimedia Integration Language (SMIL) and MathML.
Note. Not all browsers or multimedia tools may
support the features described in the guidelines. In particular,
new features of HTML 4.0 or CSS 1 or CSS 2 may not be supported.
To help readers find out about support,
the Techniques Document includes:
The Techniques Document will be updated more regularly than the
current document in order to track changes in technology.
This document is available in the following formats:
- HTML:
-
http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316/wai-pageauth.html
- A plain text file:
-
http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316/wai-pageauth.txt,
- HTML (Guidelines, List of Checkpoints, Techniques)
as a gzip'ed tar file :
-
http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316/wai-pageauth.tgz,
- HTML (Guidelines, List of Checkpoints, Techniques)
as a zip archive:
-
http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316/wai-pageauth.zip,
- A PostScript file:
-
http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316/wai-pageauth.ps,
- A PDF file:
-
http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316/wai-pageauth.pdf.
The definitive version of this document is the HTML version.
Additional appendix: List of Checkpoints for the Web Content Accessibility Guidelines.
For those unfamiliar with accessibility issues pertaining to
Web page design, consider that many users may be operating
in contexts very different from your own:
- They may not be able to see, hear, or move.
may not be able to process some types of
information easily or at all.
- They may have difficulty reading or comprehending text.
- They may not have or be able to use a keyboard or mouse.
- They may have a text-only screen, a small screen, or
a slow Internet connection.
- They may not speak or understand fluently
the language in which the document is written.
- They may be in a situation where their eyes, ears, or
hands are busy or interfered with (e.g., driving to work,
working in a loud environment, etc.).
- They may have an early version of a browser, a different
browser entirely, a voice browser, or a
different operating system.
Content developers must consider these
different situations during page design. While there are several
situations to consider, each accessible design choice generally
benefits several disability groups at once and the Web community as a
whole. For example, by using style
sheets to control font styles and eliminating the FONT element,
HTML authors will have more control over their pages, make those
pages more accessible to people with low vision, and by sharing the
style sheets, will often shorten page download times for all
users.
The guidelines discuss accessibility issues and provide
accessible design solutions. They enumerate typical scenarios
(similar to the font style example) that may pose problems for users
with certain disabilities. For example, the first guideline explains how content
developers can make images accessible. Some users may not be able to see
images, others may use text-based browsers that do not support
images, while others may have turned off support for images (e.g.,
due to a slow Internet connection). The guidelines do not suggest
avoiding images as a way to improve accessibility. Instead,
they explain that providing a text
equivalent that states the purpose of the image will make it
accessible.
How does a text equivalent make the image accessible? Users
with blindness or low vision can understand the function of the
image when the text is read aloud by a speech synthesizer. This is
particularly important when the image is part of a hyperlink since,
without an explanation of the link's destination, a user with
blindness wouldn't know whether to follow it. In addition to
benefitting users with disabilities, text equivalents can be used
by search robots when indexing your pages.
The guidelines address two general themes: ensuring graceful
transformation, and making content understandable and navigable.
By following these guidelines, content developers can create pages
that transform gracefully. Pages that transform gracefully remain
accessible despite any of the constraints described in the introduction, including physical, sensory,
and cognitive disabilities, work constraints, and technological
barriers. Here are some keys to designing pages that transform
gracefully:
- Separate content from structure from
presentation. The appendix explains
the
difference between content,
structure, and presentation).
- Provide text (including text equivalents, and text descriptions). Textual information
can be rendered in ways that are available to almost all browsing
devices and accessible to almost all users.
- Create documents that only work even if the user
cannot see and/or hear. Some content will be
sensory-specific (e.g., audio, video,
applets that present visual information), so
provide equivalent information in forms suited to other
senses as well. Note.
This does not mean creating an
entire auditory version of
a site. Screen readers will be able to speak all
information on a page as long as it is available in text.
- Create documents that do not rely on one type of hardware.
Pages should be usable by people
without mice, with small screens, low resolution screens,
black and white screens, no screens, with only voice or text
output, etc.
The theme of graceful transformation is addressed primarily by
guidelines 1 to 13.
Content developers should make content understandable and
navigable. This includes not only making the language clear and
simple, but also providing understandable features for navigating
within and between pages. Providing navigation tools and orientation
information in pages will maximize accessibility and usability.
Remember, not all users can make use of visual clues such as image
maps, proportional scroll bars, side-by-side frames, or graphics that
guide sighted users of graphical desktop browsers. Users also lose
contextual information when they can only view a portion of a page,
either because they are accessing the page one word at a time (speech
synthesis or
braille display), or one section at a time (small display,
or a magnified display). Very large tables, lists, menus, etc. without
orientation information may be very disorienting to users.
The theme of making content understandable and navigable is
addressed primarily in guidelines 14 to
16.
This document includes sixteen guidelines, or general principles of
accessible design. Each guideline is followed by a more detailed
statement of the principle and the rationale behind the guideline.
The most important part of each guideline is the list of checkpoints explaining how the guideline
applies in typical content development scenarios. Each checkpoint definition
links to a section of the Techniques Document where
implementations and examples of the checkpoint are discussed.
Each checkpoint is specific enough so that someone reviewing a page
or site may verify that the checkpoint has been satisfied.
Each checkpoint has priority level assigned by the Working
Group based on the checkpoint's impact on accessibility.
- [Priority 1] or [Priority One]
- 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] or [Priority Two]
- 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] or [Priority Three]
- 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.
This document defines three conformance levels:
- Conformance Level A: A document
or process satisfies all Priority 1 checkpoints, or
- Conformance Level Double-A: A document
or process satisfies all Priority 1 and 2 checkpoints, or
- Conformance Level Triple-A:
A document or process satisfies all Priority 1, 2,
and 3 checkpoints.
Claims of conformance to this document must provide the following
information:
- Which conformance level has been achieved: (
Conformance Level A, Double-A, or Triple-A)
- The title of this Guidelines document: "Web Content Accessibility Guidelines"
- The URI of this Guidelines document, which must be written like
this: http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316
Following is an example of a conformance claim:
The page available at http://www.something.com/document/cover.html
meets Conformance Level Double-A as defined in "Web Content Accessibility Guidelines",
located at http://www.w3.org/WAI/GL/WD-WAI-PAGEAUTH-19990316.
A text
equivalent describes the purpose or function of an image,
applet, image map, or other information.
If text equivalents are not provided for visual information, people
who are blind, have low vision, or
any user who cannot or has chosen not to view
graphics will not know the purpose of the visual components
on the page.
The Techniques Document
explains how to write text equivalents specifically for images used as
image maps, as spacers, as bullets in lists,
as
graphical buttons, as links, or
to present
mathematical equations.
- 1.1 Provide text equivalents for all images [Priority 1]
- For example, in HTML,
specify a text equivalent
via the "alt" attribute of the
IMG and INPUT elements, or for OBJECT, via
the element's content.
- Techniques for checkpoint 1.1
- 1.2 Provide text equivalents for all applets and other programmatic objects. [Priority 1]
- For example, in HTML, provide
a text equivalent for OBJECT
via the element's content. Also in HTML, for APPLET,
specify it via the "alt" attribute or within the content of the
element.
- Refer also to checkpoint 8.5 and guideline 10.
- Techniques for checkpoint 1.2
- 1.3 For short animations such as "animated gifs," provide a text equivalent and a description if needed. [Priority 1]
- Refer also to guideline 2.
- Techniques for checkpoint 1.3
- 1.4 Provide a text equivalent for each active region of an image map. [Priority 1]
- For example, in HTML,
provide information via the "alt" attribute of the AREA element or the
MAP element with A elements as content.
- Techniques for checkpoint 1.4
- 1.5 Provide client-side image maps instead of server-side image maps except where the regions cannot be defined with an available geometric shape. [Priority 1]
- Techniques for checkpoint 1.5
- 1.6 Replace ASCII art with an image or describe the ASCII art and provide a means (e.g., a link) to skip over it. [Priority 1 or Priority 2 depending on the importance of the information.]
- Note. When replacing
ASCII art with an image, specify
a text equivalent for
the image. The guidelines includes
an example of ascii art.
- Techniques for checkpoint 1.6
- 1.7 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. Content developers will not need to provide redundant text links for client-side image maps once most user agents render text equivalents for the map links.]
- Note. If the description of
important ASCII art is long, provide a description in addition to
a text equivalent. Refer also to guideline 2.
- Techniques for checkpoint 1.7
- 1.8 Provide individual button controls in a form rather than simulating a set of buttons with an image map. [Priority 2]
- Techniques for checkpoint 1.8
Note. When a button has an image, specify text equivalent
for the image.
A description provides information about
the appearance or sound of an image, script, or applet. Descriptions
make information presented graphically (charts, billboards, diagrams)
perceivable to people with blindness, some people with low vision, and
to people who have chosen not to view graphics, scripts, or applets or
whose browser does not support scripts or applets.
In movies or visual presentations, visual action such as body
language or other visual cues may not be accompanied by enough audio
information to convey the same information. Unless verbal descriptions
of this visual information are provided, people who cannot see (or
look at) the visual content will not be able to perceive it.
If a visual presentation has an associated auditory presentation
(e.g., a movie), synchronize the audio version of the descriptions
with the existing auditory presentation, and collate a text version of
the descriptions with the text transcripts (captions) of the primary
audio track. The collated
information will make the presentation available to people who are
deaf-blind and to people who cannot play or choose not to play movies,
animations, etc.
- 2.1 Provide a description of each graphic, script, or applet that conveys important information. [Priority 1]
- For example, in HTML, for IMG
specify a description via "longdesc" and for OBJECT
within the element's content. Or, put a
description link in the document.
- Techniques for checkpoint 2.1
- 2.2 For movies, provide auditory descriptions that are synchronized with the original audio. [Priority 1]
- Techniques for checkpoint 2.2
When a transcript is synchronized with a video presentation it is
called a "caption". Captions are used by people who cannot hear the
audio track of the video material. Without transcripts and captions,
people who are deaf, or hard of
hearing, or any user who cannot or has chosen not to
hear sound cannot perceive the information presented through
speech, sound effects, music, etc.
- 3.1 For stand-alone audio files, provide a text transcript of all words (spoken or sung) and all important sounds. [Priority 1]
- Techniques for checkpoint 3.1
- 3.2 For audio associated with video, synchronize the text transcript with the video. [Priority 1]
- Synchronize
the transcript (of dialog and sounds) as a caption.
- Techniques for checkpoint 3.2
- 3.3 Where sounds are played automatically, provide visual notification and transcripts. [Priority 1 or Priority 2 depending on the importance of the sound.]
- Techniques for checkpoint 3.3
- 3.4 Provide a text version of the auditory description and collate it with the text transcript (captions) of the primary audio track. [Priority 2]
- Techniques for checkpoint 3.4
If color alone is used to convey information, people who cannot
differentiate between certain colors and users with devices that have
non-color or non-visual displays will not receive the information.
When foreground and background colors are too close to the same
hue, they may not provide sufficient contrast when viewed using
monochrome displays or by people with different types of color
deficits.
- 4.1 Ensure that all information conveyed with color is also available without color, for example from context or markup. [Priority 1]
- When text has a purely decorative value and conveys
no information other than the color itself, it is not necessary
to provide that information elsewhere.
- Techniques for checkpoint 4.1
- 4.2 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]
- Techniques for checkpoint 4.2
Using markup improperly -- not according to specification --
hinders accessibility. Misusing markup for a presentation effect
(e.g., using a table for layout or a header to change the font size)
makes it difficult for users with specialized
software to understand the organization of the page or to
navigate through it. Furthermore, presentation effects used alone to
convey (e.g., constructing what looks like a table of data
with an HTML PRE element) make it difficult to render a page
intelligibly to other devices (refer to the description of
difference between content,
structure, and presentation).
Content developers
may be tempted to use (or misuse) constructs that achieve a
desired formatting effect on older browsers. They must be aware that
these practices cause accessibility problems and must consider
whether the formatting effect is so critical as to make the document
inaccessible to some users.
At the other extreme, content developers
must not sacrifice correct
markup because they are concerned about the accessibility problems it
might cause. For example, it is appropriate to use
the TABLE element in HTML to mark up tabular data. Doing so (and
creating tables that transform
gracefully (refer to guideline 7)
make it possible for software to render tables
other than as two-dimensional grids.
- 5.1 Use header elements to convey logical structure and use them according to specification. [Priority 2]
- For example, in HTML, use H2 to indicate
a subsection of H1. Do not use headers for font effects.
- Techniques for checkpoint 5.1
- 5.2 Mark up lists and list items properly. [Priority 2]
- For example, in HTML, nest OL, UL, and DL lists properly.
- Techniques for checkpoint 5.2
- 5.3 Mark up quotations. Do not use quotation markup for formatting effects such as indentation. [Priority 2]
- For example, in HTML, use the Q and BLOCKQUOTE elements
to markup short and longer quotations, respectively.
- Techniques for checkpoint 5.3
- 5.4 Create documents that validate to published formal grammars. [Priority 2]
- For example, include a document type declaration at the
beginning of a document that refers to a published DTD.
- Techniques for checkpoint 5.4
- 5.5 Use style sheets to control layout and presentation. [Priority 2]
- For example, use the CSS 'font' property
instead of the HTML FONT element to control font styles.
- Techniques for checkpoint 5.5
- 5.6 When an appropriate markup language exists, use markup rather than images to convey information. [Priority 2]
- For example, use MathML to mark up mathematical
equations, and
style sheets to format text and control layout. Also,
avoid using images to represent text - use text and style sheets
instead.
- Note. If important information
is conveyed in many images on the page, provide an
alternative
accessible page. Refer also to
guideline 8 and
guideline 13.
- Techniques for checkpoint 5.6
- 5.7 Use relative rather than absolute units in markup language attribute values and style sheet property values. [Priority 2]
- For example, in CSS, use 'em' or percentage
lengths rather than 'pt' or 'cm', which are absolute
units.
- Techniques for checkpoint 5.7
Changes between multiple languages on the same page and
abbreviations can both be indecipherable when machine-spoken or
brailled unless they are identified. Content developers should
identify the predominant natural language of a document's text and
indicate when language changes occur. They should also provide
expansions of abbreviations and acronyms. This information also helps
search engines find key words and identify documents in a desired
language. The information also improves readability of the Web for all
people, including those with learning disabilities, cognitive
disabilities, and deafness.
- 6.1 Clearly identify changes in the natural language of a document's text. [Priority 1]
- For example, in HTML
use the "lang" attribute. In XML, use "xml:lang".
Server operators should configure their server to
take advantage of the content negotiation mechanisms
of the HTTP protocol so
that clients can automatically retrieve
documents of the preferred language.
- Techniques for checkpoint 6.1
- 6.2 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.]
- For example, in HTML,
use the "title" attribute of the ABBR and ACRONYM elements.
- Techniques for checkpoint 6.2
- 6.3 Identify the primary natural language of a document. [Priority 3]
- For example, in HTML, set the "lang"
attribute on the HTML element. In XML, use "xml:lang".
- Techniques for checkpoint 6.3
Tables should be used to mark up truly tabular data
("data tables"). Content developers should avoid using them
to lay out pages ("layout tables").
Tables for any use also present special
problems to users of screen
readers.
Many user agents transform tables to
present them and if not marked up properly, the tables will not make
sense when rendered. Refer also to guideline 5.
The following checkpoints will directly benefit people who access a
table through auditory means (e.g., a screen reader or an Automobile
PC that operates by speech input and output) or who view only a
portion of the page at a time (e.g., users with blindness or low
vision using speech output or a braille display, or other users of
devices with small displays, etc.).
- 7.1 For data tables, identify headers for rows and columns. [Priority 1]
- For example, in HTML, use TD to
identify data cells and TH to identify headers.
- Techniques for checkpoint 7.1
- 7.2 For data tables that have more than one row and/or more than one column of header cells, use markup to associate data cells and header cells. [Priority 1]
- For example, in HTML, use THEAD, TFOOT, and TBODY to group
rows, COL and COLGROUP to group columns, and
the "axis", "scope", and "headers" attributes, to describe
more complex relationships among data.
- Techniques for checkpoint 7.2
- 7.3 Avoid using tables for layout. [Priority 2]
- Techniques for checkpoint 7.3
- 7.4 If a table is used for layout, do not use any structural markup for the purpose of visual formatting. [Priority 2]
- For example, in HTML do not use the TH element to
cause the content of a (non-table header)
cell to be displayed centered and in bold.
Use the "summary" attribute to explain
that the table is a layout table.
- Techniques for checkpoint 7.4
- 7.5 Provide summaries for tables. [Priority 3]
- For example, in HTML, use the "summary" attribute
of the TABLE element.
- Techniques for checkpoint 7.5
- 7.6 Provide abbreviations for header labels. [Priority 3]
- For example, in HTML, use the "abbr" attribute on the TH
element.
- Techniques for checkpoint 7.6
Refer also to checkpoint 12.3
and checkpoint 5.6.
Although content developers
are encouraged to use new technologies that
solve problems raised by existing technologies, they should know how
to make their pages still work with older browsers
and people who choose to turn off features.
- 8.1 Ensure that descriptions and text alternatives for dynamic content are updated when the dynamic content changes. [Priority 1]
- Techniques for checkpoint 8.1
- 8.2 For scripts that present important information or functionality, provide an equivalent. (Refer to the definition of equivalent.) [Priority 1]
- For example, in HTML use NOSCRIPT or a
server-side script that outputs the equivalent.
- Techniques for checkpoint 8.2
- 8.3 For pages that use style sheets or presentation markup, ensure that the content of each page is organized logically. [Priority 1]
- This makes it more likely that the document will be
understood even when styles are turned off or overridden by the user.
For applets and programmatic objects,
provide text equivalents and
descriptions.
- Techniques for checkpoint 8.3
- 8.4 Provide an alternative presentation or page when the primary content is dynamic. [Priority 2]
- For example: In HTML, use
NOFRAMES at the end of each frameset, NOSCRIPT
for every script, and server-side instead
of client-side scripts.
- Techniques for checkpoint 8.4
- 8.5 Provide non-text equivalents for all applets and other programmatic objects. [Priority 2]
- For example, for an animation, one might provide a snapshot of the
animation. For an applet, one might provide a video equivalent.
This checkpoint is helpful for people whose browsers
cannot run the applets or programmatic objects but who can perceive
visual presentations. It can also be helpful to non-readers, including
deaf non-readers. For example, for an applet, one might provide a video
equivalent of a person communicating the content using a manual
communication system (e.g., sign language).
- Refer also to checkpoint 1.2.
- Techniques for checkpoint 8.5
Refer also to checkpoint 13.4.
Some people with cognitive or
visual disabilities are unable to read moving text
quickly enough or at all. Movement can also cause such a distraction
that the rest of the page becomes unreadable for people with
cognitive disabilities. Screen
readers are unable to read moving text. People with
physical disabilities might not be able to move
quickly or accurately enough to interact with moving objects. People
with photosensitive epilepsy can have seizures 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).
- 9.1 Until user agents provide the ability to stop the refresh, do not create periodically auto-refreshing pages [Priority 1]
- For example, in HTML, don't
cause pages to auto-refresh
with "HTTP-EQUIV=refresh" until user agents
allow users to turn off that feature.
- Techniques for checkpoint 9.1
- 9.2 Avoid any blinking or updating of the screen that causes flicker. [Priority 1]
- Techniques for checkpoint 9.2
- 9.3 Avoid movement in pages. When a page includes moving content, provide a mechanism to allow users to freeze motion or updates in applets and scripts or use style sheets and scripting to create movement. [Priority 2]
- Note. Style sheets and scripts can be turned
off or overridden.
- Refer also to guideline 10.
- Techniques for checkpoint 9.3
- 9.4 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. [Priority 2]
- Techniques for checkpoint 9.4
Note. The BLINK and MARQUEE elements are not
defined in any W3C HTML specification and should not be
used. Refer also to guideline 13.
When an embedded object has its "own interface", the interface --
like the interface to the browser itself -- must be accessible. If the
interface of the embedded object cannot be made accessible, an
alternative accessible solution must be provided.
Note. For information about accessible interfaces,
please consult the User Agent Accessibility Guidelines ([WAI-USERAGENT]), the Authoring Tool
Accessibility Guidelines ([WAI-AUTOOL]), and the discussion of applets and other objects in
the Techniques Document.
- 10.1 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 also to guideline 8.
- Techniques for checkpoint 10.1
Interaction with a document must not depend on a particular input
device; remember not everyone uses a mouse. If, for example, a form
control can only be activated with a mouse or other pointing device,
someone who is using the page without sight, with voice input, or with
a keyboard or who is using an input device other than a mouse (e.g., a
braille
display) will not be able to use the form.
Note. Providing text equivalents for image maps or
images used as links makes it possible for users to interact with them
without a pointing device. Refer also to guideline 1.
Generally, pages that allow keyboard interaction are
also accessible through speech input or a command line interface.
- 11.1 Ensure that all elements that have their own interface are keyboard operable. [Priority 2]
- Refer also to guideline 10.
- Techniques for checkpoint 11.1
- 11.2 For scripts, specify logical event handlers rather than device-dependent event handlers. [Priority 2]
- For example, in HTML use "onfocus", "onblur", and "onselect".
- Techniques for checkpoint 11.2
- 11.3 Create a logical tab order through links, form controls, and objects. [Priority 3]
- For example, in HTML, specify tab order via the
"tabindex" attribute or ensure a logical page design.
- Techniques for checkpoint 11.3
- 11.4 Provide keyboard shortcuts to links, including those in client-side image maps, form controls, and groups of form controls. [Priority 3]
- For example, in HTML, specify shortcuts
via the "accesskey" attribute.
- Techniques for checkpoint 11.4
For example, older browsers do not allow users to
navigate to empty edit boxes. Older screen readers read lists of
consecutive links as one link. These active elements are therefore
difficult or impossible to access. Also, changing the current window
or popping up new windows can be very disorienting to users
who have available, but aren't using, the graphical features of the
desktop environment.
Note. The following checkpoints apply until most
users are able to secure newer technologies that address these
issues.
- 12.1 Do not cause pop-ups or other windows to appear and do not change the current window without informing the user. [Priority 2]
- For example, in HTML, avoid using a frame whose target
is a new window.
- Techniques for checkpoint 12.1
- 12.2 For all form controls with implicitly associated labels, ensure that the label is properly positioned. [Priority 2]
- The label must immediately precede
its control on the same line (allowing more than one
control/label per line) or be in the line preceding the
control (with only one label and one control per line).
- Techniques for checkpoint 12.2
- 12.3 Provide a linear text alternative (on the current page or some other) for all tables that lay out text in parallel, word-wrapped columns. [Priority 2]
- Note.
This checkpoint benefits people with
user agents
(such as some screen readers)
that are unable to handle blocks of text presented side-by-side.
- Techniques for checkpoint 12.3
- 12.4 Include default, place-holding characters in edit boxes and text areas. [Priority 3]
- For example, in HTML, do this for TEXTAREA and
INPUT.
- Techniques for checkpoint 12.4
- 12.5 Include non-link, printable characters (surrounded by spaces) between links that occur consecutively. [Priority 3]
- Techniques for checkpoint 12.5
Many non-W3C technologies (e.g., PDF, Shockwave, and other data
formats) used to encode information require either plug-ins or
stand-alone applications which often create pages that cannot be
viewed or navigated using standard Web access or screen reading tools.
Avoiding non-W3C and non-standard features (proprietary elements,
attributes, properties, and extensions) will tend to make pages more
accessible to more people using a wider variety of hardware and
software.
Even when W3C technologies are used, they must be used in
accordance with accessibility guidelines.
Note. Converting documents (from PDF, PostScript,
RTF, etc.) to W3C markup languages (HTML,
XML) does not always create
an accessible document. Therefore, test each page for
accessibility and usability
after the conversion process. If a page does not readily
convert, either revise the page until its original
representation converts appropriately or provide an HTML or plain text
equivalent.
- 13.1 If W3C technologies are used, use the latest W3C specification where it is supported. [Priority 2]
- Techniques for checkpoint 13.1
- 13.2 If W3C technologies are used, avoid deprecated language features. [Priority 2]
- Techniques for checkpoint 13.2
- 13.3 Provide information so that users may receive documents according to their preferences (e.g., language, content type, etc.) [Priority 3]
- Note.
Use content negotiation where possible.
- Techniques for checkpoint 13.3
- 13.4 If, after best efforts, you cannot avoid using a non-W3C technology or any W3C technology in an accessible way, 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. [Priority 1]
- Techniques for checkpoint 13.4
Note.
Content developers should only resort to alternative
pages when other solutions fail because alternative pages
are generally updated less often than "primary" pages. An out-of-date
page may be as frustrating as one that is inaccessible since, in both
cases, the information presented on the original page is not
available. Automatically generating alternative pages may lead to
more frequent updates, but content developers
must still be careful to ensure
that generated pages always make sense and that users are able to
navigate a site by following links on primary pages, alternative
pages, or both. Before resorting to an alternative page,
reconsider the design of the original page; simplifying it
is likely to make it more effective for all users.
Grouping and providing contextual information about the
relationships between elements can be useful for all
users. Complex relationships between elements on a page may
be difficult for people with cognitive disabilities
and people with visual disabilities to interpret.
- 14.1 Title each frame so that users can keep track of frames by title. [Priority 1]
- For example, in HTML use the "title" attribute on FRAME
elements.
- Techniques for checkpoint 14.1
- 14.2 Describe the purpose of frames and how frames relate to each other if it is not obvious by frame titles alone. [Priority 2]
- For example, in HTML, use "longdesc," or a
description link
- Techniques for checkpoint 14.2
- 14.3 Group form controls. [Priority 2 - for radio buttons and checkboxes, Priority 3 - for other controls.]
- For example, in HTML use the FIELDSET and LEGEND elements.
- Techniques for checkpoint 14.3
- 14.4 Associate labels explicitly with their controls. [Priority 2]
- For example, in HTML use LABEL and its "for" attribute.
- Techniques for checkpoint 14.4
- 14.5 Divide long lists of choices into manageable groups. [Priority 2]
- For example, in HTML use the OPTGROUP element.
- Techniques for checkpoint 14.5
Clear and consistent navigation
mechanisms will benefit not only people with cognitive
disabilities or blindness, but everyone who visits the site.
- 15.1 Make link phrases terse yet meaningful when read on their own or in succession. [Priority 2]
- Avoid general phrases, such as "click here" (which
is device-dependent in addition to saying nothing
about what is to be found at the end of the link).
- Techniques for checkpoint 15.1
- 15.2 Provide metadata to add semantic information to pages and sites. [Priority 2]
- For example, use RDF ([RDF])
to indicate the document's author,
the type of content, and to describe the navigation
mechanism, etc.
- Techniques for checkpoint 15.2
- 15.3 Provide navigation bars to highlight and give access to the navigation mechanism. [Priority 3]
- Note. Some user agents
can build navigation tools from document relations described by
the HTML LINK element and "rel" or "rev" attributes
(e.g., rel="next", rel="previous", rel="index", etc.)
- Techniques for checkpoint 15.3
- 15.4 Provide a site map or table of contents that makes the structure of a Web site apparent and facilitates navigation. [Priority 3]
- Techniques for checkpoint 15.4
- 15.5 Provide a description of the general layout of the site, the access features provided, and how to use them. [Priority 3]
- Techniques for checkpoint 15.5
- 15.6 Use navigation mechanisms in a consistent manner. [Priority 3]
- Techniques for checkpoint 15.6
- 15.7 Enable different types of searches for different skill levels and preferences. [Priority 3]
- Techniques for checkpoint 15.7
- 15.8 Place distinguishing information at the beginning of headings, paragraphs, lists, etc. [Priority 3]
- Note.
This is commonly referred to as "front-loading" and is
especially helpful for people accessing information with serial
devices such as speech synthesizers.
- Techniques for checkpoint 15.8
- 15.9 Facilitate off-line browsing by creating a single downloadable file for documents that exist as a series of separate pages. [Priority 3]
- A second option is to
provide an archive (e.g., with zip, gzip, stuffit, etc.)
of the multiple pages.
- Techniques for checkpoint 15.9
- 15.10 Group related links, identify the group (for user agents), and, until user agents do so, provide a way to bypass the group. [Priority 3]
- For example, when creating a navigation bar composed
of links in HTML use "title" on FRAME, DIV, SPAN, etc. Use class="nav"
to identify the group. Use "tabindex=1" on an anchor after
the group so users may quickly navigate to it.
- Techniques for checkpoint 15.10
Consistent page layout, recognizable graphics, and easy to understand
language benefit all who visit a site. In particular, they help
people with cognitive disabilities or who
have difficulty reading. (However, ensure that images
have text equivalents for people who are blind, have
low vision, or for any user who cannot or has
chosen not to view graphics. Refer also to guideline 1.)
Using clear and simple language promotes effective
communication. Conditions such as cognitive disabilities, learning
disabilities, and deafness can make access to written information
difficult to impossible for some users. This consideration also
applies to the many people whose first language differs from your
own.
- 16.1 Use language that is clear and simple, yet appropriate for the site's content. [Priority 1]
- Techniques for checkpoint 16.1
- 16.2 Provide icons or graphics (with text equivalents and descriptions) where they facilitate comprehension of the page. [Priority 3]
- Note. These are particularly important
for non-readers. Refer also to 1
and 2
- Techniques for checkpoint 16.2
- 16.3 Create a style of presentation that is consistent across pages. [Priority 3]
- Techniques for checkpoint 16.3
Validate accessibility with automatic tools and human
review. Automated methods are generally rapid and convenient but cannot
identify all accessibility issues. Human review can help ensure
clarity of language and ease of navigation.
Begin using validation methods at the earliest stages of
development. Accessibility issues identified early are easier to
correct and avoid.
Following are some important validation methods, discussed
in more detail in the
section on validation in the Techniques Document.
- Use an automated accessibility tool and browser validation tool.
Please not that software tools do not address all accessibility
issues, such as the meaningfulness of link text, the applicability of
a description, etc.
- Validate the HTML.
- Validate the style sheets.
- Use a text-only browser or emulator.
- Use multiple graphic browsers, with:
- sounds and graphics loaded,
- graphics not loaded,
- sounds not loaded,
- no mouse,
- frames, scripts, style sheets, and applets not loaded
- Use several browsers, old and new.
- Use a self-voicing
browser, a screen reader, magnification software, a small display,
etc.
- Use spell and grammar checkers. 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. Eliminating grammar problems
increases comprehension.
- Review content and structure
for clarity and simplicity.
Readability statistics, such as those generated by some word
processors may be useful indicators of clarity and simplicity. Better
still, ask an experienced (human) editor to review written content for
clarity. Editors can also improve the usability of documents by
identifying intercultural problems that might arise due to language or
icon usage.
- Invite people with disabilities to review your documents. Expert
and novice users with disabilities will provide valuable feedback
about accessibility or usability problems and their severity.
- Accessible
- ???
- Applet
- A program inserted into a Web page.
- ASCII art
- ASCII art refers to text characters and symbols that are
combined to create an image. For example
";-)" is the smiley emoticon and the following drawing
represents a cow (skip cow):
(__)
(oo)
/-------\/
/ | ||
* ||----||
- Authoring tool
- HTML editors, document conversion tools, tools that
generate Web content from databases. Refer to the
"Authoring Tool Accessibility Guidelines" ([WAI-AUTOOLS]) for information about developing
accessible tools.
- Backward compatible
- Something that has been designed to work with earlier versions
of a language, program, etc.
- Braille
- Braille uses six raised dots in different patterns to represent
letters and numbers to be read by people who are blind with their
fingertips. The word "Accessible" in braille follows:
- A braille display,
commonly referred to as a "dynamic braille display," raises or lowers
dot patterns on command from an electronic device, usually a
computer. The result is a line of braille that can change from moment
to moment. Dynamic braille displays range in size from one cell (six
or eight dots) to an eighty cell line. Displays with twelve to twenty
cells per line are the most common.
- Collate
- When referring to
transcripts, collating means combining
the text version of the descriptions and the text
transcript (captions) of the primary audio track into
a single document to read like a script of the movie. In other
words, the two documents are not combined but flow as a single
document.
- Content/Structure/Presentation
- The content of a document refers to both what the document says
and the bytes (text and markup) that make it up. The structure of a
document is how it is organized logically (e.g., by chapter, with an
introduction and table of contents, etc.) The presentation of a
document is how the document is rendered (e.g., as print, as a
two-dimensional graphical presentation, as an text-only presentation,
as synthesized speech, as braille, etc.
-
Consider a header, for example. The content of the header
is what the header says (e.g., "Sailboats") and how it
is marked up (e.g., with an H2 element in HTML). In terms
of structure, the header may be part of a chapter of the
document. Finally, the presentation of the header might be
a bold block text in the margin, a centered line of text,
a title spoken with a certain voice style (like an aural
font), etc.
- Content
developer
- Someone who authors Web pages or designs Web sites.
- Dynamic
HTML (DHTML)
-
DHTML is the marketing term applied to
a mixture of standards including HTML,
style sheets, the
Document Object Model [DOM1]
[DOM1] and scripting.
However, there is no W3C specification that formally defines DHTML. Most guidelines may be applicable
to applications using DHTML, however the following guidelines focus on
issues related to scripting, and style sheets: guideline 1,
guideline 2, guideline 8, and guideline 9.
- Equivalent
and Description
- An equivalent complements a primary functionality
with a second, essentially equal functionality. For instance,
an equivalent for an image functioning as a visual navigation
arrow would convey information about navigation. Equivalents
are important to users who, because of disability, technological
constraints, or other circumstances, cannot or choose not to access the
primary functionality in a more conventional way. Equivalents must
be provided for images, image maps, tables (through captions), and
applets.
- A description provides information about the visual
appearance or sound of content. Descriptions are generally longer than
equivalents and may be external to a document (referenced by
attributes such as "longdesc" or by inline markup, called description links, or
d-links). Descriptions should be provided for audio and video clips,
complex tables, images where detail is required, etc. Descriptions may
provide information about functionality, but if the information is
short, an equivalent should be used instead.
- A text
equivalent or text description is expressed
in actual characters, making the information available for visual,
braille, or speech output.
- A non-text equivalent or non-text
description is expressed in other media. Examples of non-text
equivalents include graphical, video, pre-recorded audio
equivalents. An example of a video equivalents would be videos of sign
language renderings of the content. Non-text equivalents are
particularly important for non-readers with deafness.
- Image
- A graphical presentation.
- Image map
- An image that has been divided into regions with associated
actions. Clicking on an active region causes an action to occur.
- When a user clicks on an active region of a
client-side image map,
the user agent calculates in which region the click occurred and
follows the link associated with that region.
Clicking on an active
region of a server-side image map causes the coordinates of the click
to be sent to a server, which then performs some action.
- Content developers
can make client-side image maps accessible by providing
device-independent access to the same links associated with the image
map's regions. Client-side image maps allow the user agent to provide
immediate feedback as to whether or not the user's pointer is over an
active region.
- Important
- Information is important if understanding it in detail is
necessary for the overall understanding of a document.
- Navigation Mechanism
- A navigation mechanism is any means by which a user can
navigate a page or site. Some typical mechanisms include:
- navigation bars
- A navigation bar is a collection of links
to the most important parts of a document or site.
- site maps
- A site map provides a global view of the
organization of a page or site.
- tables of contents
- A table of contents generally lists
(and links to) the most important sections of a document.
- Personal Digital Assistant
(PDA)
- A PDA is a small,
portable computing device. Most PDAs are used to track personal data
such as calendars, contacts, and electronic mail. A PDA is generally a
handheld device with a small screen that allows input from various
sources.
- Screen
magnifier
- A software program that magnifies a portion of the screen, so
that it can be more easily viewed. Screen magnifiers
are used primarily by individuals
with low vision.
- Screen reader
- A software program that reads the contents of the screen aloud
to a user. Screen readers are used primarily
by individuals who are blind, screen
readers can usually only read text that is printed, not painted, to
the screen.
- Style sheets
- A style sheet is a set of statements that specify presentation of
a document. Style sheets may have three different origins: they
may be written by content providers, created by users, or
built into user agents. In CSS ([CSS2]),
the interaction of content provider, user, and user agent
style sheets is called the cascade.
- Presentation markup is markup
that achieves a stylistic (rather than structuring) effect
such as the B or I elements in HTML. Note that the STRONG
and EM elements are not considered presentation markup since
they convey information that is independent of a particular
font style.
- User agent
- Software to access Web content, including desktop graphical
browsers, text browsers,
voice browsers, mobile phones, multimedia players, plug-ins,
and assistive technologies such as screen readers and screen
magnifiers.
- WAI Markup 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 G. 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.
- [CSS1]
- "CSS, level 1 Recommendation", B. Bos, H. Wium Lie, eds. The
CSS1 Recommendation is available at:
http://www.w3.org/TR/1999/REC-CSS1-19990111.
- [CSS2]
- "CSS, level 2 Recommendation", B. Bos, H. Wium Lie, C. Lilley,
and I. Jacobs, eds. The CSS2 Recommendation is available at:
http://www.w3.org/TR/1998/REC-CSS2-19980512.
- [DOM1]
- "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. The DOM Level 1
Recommendation is available at:
http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001.
- [HTML40]
- "HTML 4.0 Recommendation", D. Raggett, A. Le Hors, and I.
Jacobs, eds. The HTML 4.0 Recommendation is available at:
http://www.w3.org/TR/1998/REC-html40-19980424.
- [HTML32]
- "HTML 3.2 Recommendation", D. Raggett, ed. The HTML 3.2
Recommendation is available at:
http://www.w3.org/TR/REC-html32.
- [MATHML]
- "Mathematical Markup Language", P. Ion and R. Miner, eds. The MathML 1.0
Recommendation is available at:
http://www.w3.org/TR/1998/REC-MathML-19980407.
- [PNG]
- "PNG (Portable Network Graphics) Specification", T. Boutell, ed.,
T. Lane, contributing ed. The PNG Recommendation is available at:
http://www.w3.org/TR/REC-png.
- [RDF]
- "Resource Description Framework
(RDF) Model and Syntax Specification", O. Lassila, R. Swick,
eds. The RDF Recommendation is available at:
http://www.w3.org/TR/1999/REC-rdf-syntax-19990222.
- [SMIL]
- "Synchronized Multimedia Integration Language (SMIL) 1.0
Specification", P. Hoschka, editor. The SMIL 1.0 Recommendation is
available at:
http://www.w3.org/TR/1998/REC-smil-19980615
- [WAI-AUTOOLS]
- "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/
- [WAI-USERAGENT]
- "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/
- [UWSAG]
- "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
- [XML]
- "Extensible Markup Language (XML) 1.0.", T. Bray, J. Paoli, C.M.
Sperberg-McQueen, eds. The XML 1.0 Recommendation is available at:
http://www.w3.org/TR/1998/REC-xml-19980210
