4. Documents shall be organized so they are readable without requiring an associated style sheet. (508:D. W3C: 6.1 Priority 1)
What are the problems posed by style sheets?
Style sheets can enable users to define specific viewing preferences to accommodate their
disability. For instance, users with low vision may create their own style sheet so that,
regardless of what web pages they visit, all text is displayed in an extra large font with white
characters on a black background. If designers set up their pages to override user-defined
style sheets, people with disabilities may not be able to use those pages. For good access,
therefore, it is critical that designers ensure that their web pages do not interfere with user-defined
style sheets.
In general, the "safest" and most useful form of style sheets are "external" style sheets, in which the style rules are set up in a separate file. An example of source code for an external style sheet is:
<link rel="stylesheet" type="text/css" href="css/section508.css" />
