HTML and CSS Reference
In-Depth Information
WAI Guidelines
Priority
1. Provide equivalent alternatives to auditory and visual content
1.1
Provide a text equivalent for every nontext element (e.g., via
alt
,
longdesc
, or in ele-
ment 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.
1
1.2
Provide redundant text links for each active region of a server-side image map.
1
1.3
Until 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.
1
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.
1
3
1.5
Until 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.
2. Don't rely on color alone
2.1
Ensure that all information conveyed with color is also available without color, for
example from context or markup.
1
2.2
Ensure that foreground and background color combinations provide sufficient con-
trast when viewed by someone having color deficits or when viewed on a black and
white screen. [Priority 2 for images, Priority 3 for text].
2
3. Use markup and style sheets and do so properly
3.1
When an appropriate markup language exists, use markup rather than images to
convey information.
2
3.2
Create documents that validate to published formal grammars.
2
3.3
Use style sheets to control layout and presentation.
2
3.4
Use relative rather than absolute units in markup language attribute values and style
sheet property values.
2
3.5
Use header elements to convey document structure and use them according to
specification.
2
3.6
Mark up lists and list items properly.
2
3.7
Mark up quotations. Do not use quotation markup for formatting effects such as
indentation.
2
4. Clarify natural language usage
4.1
Clearly identify changes in the natural language of a document's text and any text
equivalents (e.g., captions).
1
4.2
Specify the expansion of each abbreviation or acronym in a document where it
first occurs.
3
4.3
Identify the primary natural language of a document.
3
5. Create tables that transform gracefully
5.1
For data tables, identify row and column headers.
1
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.
1
2
5.3
Do not use a table for layout unless the table makes sense when linearized. If a table
does not make sense, provide an alternative equivalent (which may be a linearized
version).
5.4
If a table is used for layout, do not use any structural markup for the purpose of visual
formatting.
2
