HTML and CSS Reference
In-Depth Information
• Use bright colors, which are the easiest for color blind users to distinguish.
• Provide a grayscale or black and white alternative for your color blind users, and be
sure that your link to that page is easily viewable.
Several sites on the Web include tools you can use to test your Web site for color
blind accessibility. You can also load color palettes into your graphics software to see
how your images will appear to users with different types of color blindness.
Style Sheets
By controlling how a page is rendered in a browser, style sheets play an important role
in making the Web accessible to users with disabilities. Many browsers, such as Internet
Explorer, allow a user to apply their own customized style sheet in place of the style sheet
specifi ed by a Web page's designer. This is particularly useful for visually impaired users who
need to display text in extra large fonts with a high contrast between the text and the back-
ground color (yellow text on a black background is a common color scheme for such users).
In order to make your pages accessible to those users, Section 508 guidelines state that
§1194.22 (d) Documents shall be organized so they are readable without requiring an
associated style sheet.
To test whether your site fulfi lls this guideline, you should view the site without the
style sheet. Some browsers allow you to turn off style sheets; alternately, you can redirect
a page to an empty style sheet. You should modify any page that is unreadable without
its style sheet to conform with this guideline.
Image Maps
Section 508 provides two standards that pertain to image maps:
§1194.22 (e)
Redundant text links shall be provided for each active region of a
server-side image map.
and
§1194.22 (f)
Client-side image maps shall be provided instead of server-side image
maps except where the regions cannot be defi ned with an available
geometric shape.
In other words, the
preferred
image map is a client-side image map, unless the map
uses a shape that cannot be defi ned on the client side. Since client-side image maps
allow for polygonal shapes, this should not be an issue; however if you must use a
server-side image map, you need to provide a text alternative for each of the map's links.
Because server-side image maps provide only map coordinates to the server, this text
is necessary in order to provide link information that is accessible to blind or visually
impaired users. Figure B-6 shows a server-side image map that satisfi es the Section 508
guidelines by repeating the graphical links in the image map with text links placed below
the image.
Figure B-6
Making a server-side image map accessible
