This document is the gateway to a series of related documents that provide
techniques for satisfying the requirements defined in "Web Content
Accessibility Guidelines 1.0" [WCAG10]. This series includes:
"Techniques for Web Content Accessibility Guidelines 1.0", the
current document, which is the gateway to the other documents.
"Core Techniques for Web Content Accessibility Guidelines 1.0"
([WCAG10-CORE-TECHNIQUES]),
which discusses the accessibility themes and general techniques that apply
across technologies (e.g., validation,
testing, etc.).
"HTML Techniques for Web Content Accessibility Guidelines 1.0"
([WCAG10-HTML-TECHNIQUES]),
which provides examples and strategies for authoring accessible Hypertext
Markup Language (HTML) content.
"CSS Techniques for Web Content Accessibility Guidelines 1.0"
([WCAG10-CSS-TECHNIQUES]),
which provides examples and strategies to help authors write Cascading Style
Sheets (CSS) as part of
accessible content design.
This version has been published to correct some broken links in the previous
version.
The 6 November 2000 version of this document is a Note in a series of Notes
produced and endorsed by the Web Content
Accessibility Guidelines Working Group. This Note has not been reviewed or
endorsed by W3C Members. The series of documents supersedes the 5 May 1999 W3C
Note "Techniques for Web Content Accessibility Guidelines 1.0". That single
document has been divided into technology-specific documents that may evolve
independently. Smaller technology-specific documents also allow authors to
focus on a particular technology.
While the "Web Content Accessibility Guidelines 1.0" Recommendation [WCAG10] is a
stable document, this series of companion documents is expected to evolve as
technologies change and content developers discover more effective techniques
for designing accessible Web sites and pages. In the near future, the Working
Group intends to incorporate techniques for the Synchronized Multimedia
Integration Language (SMIL) [SMIL] described in
"Accessibility Features of SMIL" ([SMIL-ACCESS]) and techniques
for Scalable Vector Graphics (SVG) [SVG] described in "Accessibility
Features of SVG" ([SVG-ACCESS]). The Working
Group also intends to incorporate techniques for non-W3C technologies such as
ECMAScript, PDF and
Flash.
Section 2 of this document reproduces the guidelines and checkpoints of the
"Web Content Accessibility Guidelines 1.0" [WCAG10]. Each guideline
includes:
The guideline number.
The statement of the guideline.
A list of checkpoint definitions. Checkpoints are ordered according to
their priority, e.g., Priority 1 before Priority
2.
Each checkpoint definition includes:
The checkpoint number.
The statement of the checkpoint.
The priority of the checkpoint.
A link back to the definition of the checkpoint in "Web Content
Accessibility Guidelines 1.0" [WCAG10]. Definitions may also
include informative notes, examples, cross references, and commentary to help
readers understand the scope of the checkpoint.
Each checkpoint is followed by one or more links to techniques in the
following documents:
"Core Techniques for Web Content Accessibility Guidelines 1.0"
([WCAG10-CORE-TECHNIQUES]),
which discusses the accessibility themes and general techniques that apply
across technologies.
"HTML Techniques for Web Content Accessibility Guidelines 1.0"
([WCAG10-HTML-TECHNIQUES]),
which provides examples and strategies for authoring accessible Hypertext
Markup Language (HTML) content.
"CSS Techniques for Web Content Accessibility Guidelines 1.0"
([WCAG10-CSS-TECHNIQUES]),
which provides examples and strategies to help authors write Cascading Style
Sheets (CSS) as part of
accessible content design.
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.
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.
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.
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, audio tracks of video, and video. [Priority�1] (Checkpoint
1.1)
1.3Until user
agents can automatically read aloud the text equivalent of a visual track,
provide an auditory description of the important information of the visual
track of a multimedia presentation.
[Priority�1] (Checkpoint
1.3)
1.4 For any time-based multimedia presentation (e.g., a movie or
animation), synchronize equivalent alternatives (e.g., captions or auditory
descriptions of the visual track) with the presentation. [Priority�1] (Checkpoint
1.4)
1.5Until user
agents render text equivalents for client-side image map links, provide
redundant text links for each active region of a client-side image map. [Priority�3] (Checkpoint
1.5)
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]. (Checkpoint
2.2)
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. [Priority�1] (Checkpoint
5.2)
5.3 Do not use tables for layout unless the table makes sense when
linearized. Otherwise, if the table does not make sense, provide an alternative
equivalent (which may be a
linearized version). [Priority�2] (Checkpoint
5.3)
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. [Priority�1] (Checkpoint
6.1)
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 information on an alternative accessible
page. [Priority�1] (Checkpoint 6.3)
7.2Until user agents allow users
to control blinking, avoid causing content to blink (i.e., change presentation
at a regular rate, such as turning on and off).
[Priority�2] (Checkpoint
7.2)
7.5Until 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] (Checkpoint
7.5)
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.] (Checkpoint
8.1)
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.
[Priority�1] (Checkpoint
9.1)
9.5 Provide keyboard shortcuts to
important links (including those in
client-side image maps), form controls, and groups of form controls. [Priority�3] (Checkpoint
9.5)
10.1Until 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. [Priority�2] (Checkpoint
10.1)
10.2Until user agents support
explicit associations between labels and form controls, for all form controls
with implicitly associated labels, ensure that the label is properly
positioned. [Priority�2] (Checkpoint
10.2)
10.3Until user agents (including
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.
[Priority�3] (Checkpoint
10.3)
10.4Until user agents handle
empty controls correctly, include default, place-holding characters in edit
boxes and text areas. [Priority�3] (Checkpoint
10.4)
11.1 Use W3C technologies when they are
available and appropriate for a task and use the latest versions when
supported. [Priority�2] (Checkpoint
11.1)
11.3
Provide information so that users may receive documents according to their
preferences (e.g., language, content type, etc.)
[Priority�3] (Checkpoint
11.3)
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 (or
functionality), and is updated as often as the inaccessible (original) page.
[Priority�1] (Checkpoint
11.4)
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
unavailable. 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;
making it accessible is likely to improve it for all users.
13.6 Group related links, identify the group
(for user agents), and, until
user agents do so, provide a way to bypass the group. [Priority�3] (Checkpoint
13.6)
13.9 Provide information about document
collections (i.e., documents comprising multiple pages.). [Priority�3] (Checkpoint
13.9)
For example, in HTML specify document collections with
the LINK element and the "rel" and "rev" attributes. Another way to create a
collection is by building an archive (e.g., with zip, tar and gzip, stuffit,
etc.) of the multiple pages.
Software or hardware that has been specifically designed
to assist people with disabilities in carrying out daily activities. Assistive
technology includes wheelchairs, reading machines, devices for grasping, etc.
In the area of Web Accessibility, common software-based assistive technologies
include screen readers, screen magnifiers, speech synthesizers, and voice input
software that operate in conjunction with graphical desktop browsers (among
other user
agents). Hardware assistive technologies include alternative
keyboards and pointing devices.
ASCII art
refers to text characters and symbols that are combined to create an image. For
example ";-)" is the smiley emoticon. The
following is an ASCII figure showing the relationship between flash frequency
and photoconvulsive response in patients with eyes open and closed [skip over ASCII
figure or consult a description of chart]:
HTML
editors, document conversion tools, tools that generate Web content from
databases are all authoring tools. Refer to the "Authoring Tool Accessibility
Guidelines 1.0" ([ATAG10]) for information about
developing accessible tools.
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. Current dynamic braille displays range in size from one
cell (six or eight dots) to an eighty-cell line, most having between twelve and
twenty cells per line.
A deprecated element or attribute is one that has been
outdated by newer constructs. Deprecated elements may become obsolete in future
versions of HTML. The index of HTML
elements and attributes in the Techniques Document indicates which elements
and attributes are deprecated in HTML 4.01.
Authors should avoid using deprecated elements and
attributes. User agents should continue to support them for reasons of backward
compatibility.
Users must be able to interact with a user agent (and the
document it renders) using the supported input and output devices of their
choice and according to their needs. Input devices may include pointing
devices, keyboards, braille devices, head wands, microphones, and others.
Output devices may include monitors, speech synthesizers, and braille
devices.
Please note that "device-independent support" does not
mean that user agents must support every input or output device. User agents
should offer redundant input and output mechanisms for those devices that are
supported. For example, if a user agent supports keyboard and mouse input,
users should be able to interact with all features using either the keyboard or
the mouse.
The content of a document refers to what it says to the
user through natural language, images, sounds, movies, animations, etc. The
structure of a document is how it is organized logically (e.g., by chapter,
with an introduction and table of contents, etc.). An
element (e.g., P, STRONG, BLOCKQUOTE in HTML) that specifies
document structure is called a structural element. 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.) An element
that specifies document presentation (e.g., B, FONT, CENTER) is called a
presentation element.
Consider a document heading, for example. The content of
the heading is what the heading says (e.g., "Sailboats"). In HTML, the heading
is a structural element marked up with, for example, an H2 element. Finally,
the presentation of the heading 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.
DHTML is the
marketing term applied to a mixture of standards including HTML, style sheets, the Document Object Model
[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 3, guideline 6, guideline 7, and guideline 9.
This document uses the term "element" both in the strict
SGML sense (an element is a syntactic construct) and more generally to mean a
type of content (such as video or sound) or a logical construct (such as a
heading or list). The second sense emphasizes that a guideline inspired by HTML
could easily apply to another markup language.
Note that some (SGML) elements have content that is
rendered (e.g., the P, LI, or TABLE elements in HTML), some are replaced by
external content (e.g., IMG), and some affect processing (e.g., STYLE and
SCRIPT cause information to be processed by a style sheet or script engine). An
element that causes text characters to be part of the document is called a text
element.
Content is "equivalent" to other content when both fulfill
essentially the same function or purpose upon presentation to the user. In the
context of this document, the equivalent must fulfill essentially the same
function for the person with a disability (at least insofar as is feasible,
given the nature of the disability and the state of technology), as the primary
content does for the person without any disability. For example, the text "The
Full Moon" might convey the same information as an image of a full moon when
presented to users. Note that equivalent information focuses on
fulfilling the same function. If the image is part of a link and
understanding the image is crucial to guessing the link target, an equivalent
must also give users an idea of the link target. Providing equivalent
information for inaccessible content is one of the primary ways authors can
make their documents accessible to people with disabilities.
As part of fulfilling the same function of content an
equivalent may involve a description of that content (i.e., what the content
looks like or sounds like). For example, in order for users to understand the
information conveyed by a complex chart, authors should describe the visual
information in the chart.
Since text content can be presented to the user as
synthesized speech, braille, and visually-displayed text, these guidelines
require text
equivalents for graphic and audio information. Text equivalents
must be written so that they convey all essential content. Non-text
equivalents (e.g., an auditory description of a visual
presentation, a video of a person telling a story using sign language as an
equivalent for a written story, etc.) also improve accessibility for people who
cannot access visual information or written text, including many individuals
with blindness, cognitive disabilities, learning disabilities, and
deafness.
Equivalent information may be provided in a number of
ways, including through attributes (e.g., a text value for the "alt" attribute
in HTML and SMIL), as part of element content (e.g., the OBJECT in HTML), as
part of the document's prose, or via a linked document (e.g., designated by the
"longdesc" attribute in HTML or a
description link). Depending on the complexity of the equivalent,
it may be necessary to combine techniques (e.g., use "alt" for an abbreviated
equivalent, useful to familiar readers, in addition to "longdesc" for a link to
more complete information, useful to first-time readers).
A text transcript is a text equivalent of audio information
that includes spoken words and non-spoken sounds such as sound effects. A caption is a text
transcript for the audio track of a video presentation that is synchronized
with the video and audio tracks. Captions are generally rendered visually by
being superimposed over the video, which benefits people who are deaf and
hard-of-hearing, and anyone who cannot hear the audio (e.g., when in a crowded
room). A collated text
transcript combines (collates) captions with text descriptions of
video information (descriptions of the actions, body language, graphics, and
scene changes of the video track). These text equivalents make presentations
accessible to people who are deaf-blind and to people who cannot play movies,
animations, etc. It also makes the information available to search
engines.
One example of a non-text equivalent is an auditory
description of the key visual elements of a presentation. The
description is either a prerecorded human voice or a synthesized voice
(recorded or generated on the fly). The auditory description is synchronized
with the audio track of the presentation, usually during natural pauses in the
audio track. Auditory descriptions include information about actions, body
language, graphics, and scene changes.
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.
A table rendering process where the contents of the cells
become a series of paragraphs (e.g., down the page) one after another. The
paragraphs will occur in the same order as the cells are defined in the
document source. Cells should make sense when read in order and should include
structural
elements (that create paragraphs, headings, lists, etc.) so the page
makes sense after linearization.
Spoken, written, or signed human languages such as French, Japanese,
American Sign Language, and braille. The natural language of content may be
indicated with the "lang" attribute in HTML ([HTML4], section 8.1) and the
"xml:lang" attribute in XML ([XML], section 2.12).
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.
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.
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.
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.
When tables are used to represent logical relationships among data -- text,
numbers, images, etc., that information is called "tabular information" and the
tables are called "data tables". The relationships expressed by a table may be
rendered visually (usually on a two-dimensional grid), aurally (often preceding
cells with header information), or in other formats.
In most of the checkpoints, content developers are asked
to ensure the accessibility of their pages and sites. However, there are
accessibility needs that would be more appropriately met by user agents (including assistive
technologies). As of the publication of this document, not all user
agents or assistive technologies provide the accessibility control users
require (e.g., some user agents may not allow users to turn off blinking
content, or some screen readers may not handle tables well). Checkpoints that
contain the phrase "until user agents ..." require content developers to
provide additional support for accessibility until most user agents readily
available to their audience include the necessary accessibility features.
Note. The WAI Web site
(refer to [WAI-UA-SUPPORT]) provides
information about user agent support for accessibility features. Content
developers are encouraged to consult this page regularly for updated
information.
Software to access Web content, including desktop
graphical browsers, text browsers, voice browsers, mobile phones, multimedia
players, plug-ins, and some software assistive technologies used in conjunction
with browsers such as screen readers, screen magnifiers, and voice recognition
software. Refer to the "User Agent Accessibility Guidelines 1.0" ([UAAG10]) for
information about developing accessible tools.
"Authoring Tool
Accessibility Guidelines 1.0", J. Treviranus, C. McCathieNevile, I. Jacobs,
and J. Richards, eds., 3 February 2000. This ATAG 1.0
Recommendation is http://www.w3.org/TR/2000/REC-ATAG10-20000203/.
"CSS, level 2
Recommendation", B. Bos, H. Wium Lie, C. Lilley, and I. Jacobs, eds., 12
May 1998. This CSS2 Recommendation is
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. This DOM Level 1 Recommendation is
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 4.01
Recommendation", D. Raggett, A. Le Hors, and I. Jacobs, eds., 24 December
1999. This HTML 4.01 Recommendation is
http://www.w3.org/TR/1999/REC-html401-19991224/.
"Accessibility Features of SMIL", M. Koivunen and I. Jacobs, eds., 21
September 1999. This W3C Note is
http://www.w3.org/TR/1999/NOTE-SMIL-access-19990921/.
"Accessibility Features of SVG", C. McCathieNevile and M. Koivunen, eds., 7
August 2000. This W3C Note is
http://www.w3.org/TR/2000/NOTE-SVG-access-20000807.
"Web Content
Accessibility Guidelines 1.0", W. Chisholm, G. Vanderheiden, and I. Jacobs,
eds., 5 May 1999. This WCAG 1.0 Recommendation is
http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505/.
"Extensible Markup
Language (XML) 1.0.", T. Bray, J. Paoli, C.M. Sperberg-McQueen, eds., 10
February 1998. This XML 1.0 Recommendation is:
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 does not guarantee the stability of any of
the following references outside of its control. These references are included
for convenience. References to products are not endorsements of those
products.
"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.
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, Chuck Letourneau,
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, and Jaap van Lelieveld
