HTML and CSS Reference
In-Depth Information
Figure B-3
Using a D-link
sales.html
<img src="chart.jpg" alt="Sales Chart" />
<a href="sales.html">D</a>
To make your pages accessible to visually-impaired users, you will probably use a
combination of alternative text and linked documents.
Multimedia
Audio and video have become important ways of conveying information on the Web.
However, creators of multimedia presentations should also consider the needs of deaf
users and users who are hard of hearing. The standard for multimedia accessibility is
§1194.22 (b) Equivalent alternatives for any multimedia presentation shall be
synchronized with the presentation.
This means that any audio clip needs to be accompanied by a transcript of the audio's
content, and any video clip needs to include closed captioning. Refer to your multimedia
software's documentation on creating closed captioning and transcripts for your video
and audio clips.
Color
Color is useful for emphasis and conveying information, but when color becomes an
essential part of the site's content, you run the risk of shutting out people who are color
blind. For this reason the third Section 508 standard states that
§1194.22 (c)
Web pages shall be designed so that all information conveyed with color
is also available without color, for example from context or markup.
About 8% of men and 0.5% of women are affl icted with some type of color blindness.
The most serious forms of color blindness are:
•
deuteranopia
: an absence of green sensitivity; deuteranopia is one example of
red-green color blindness, in which the colors red and green cannot be easily
distinguished.
•
protanopia
: an absence of red sensitivity; protanopia is another example of red-green
color blindness.
•
tritanopia
: an absence of blue sensitivity. People with tritanopia have much less loss of
color sensitivity than other types of color blindness.
•
achromatopsia
: absence of any color sensitivity.
The most common form of serious color blindness is red-green color blindness.
Figure B-4 shows how each type of serious color blindness would affect a person's view
of a basic color wheel.
