Cascading style sheets permit great design flexibility, improve site accessibility by separating page content from layout, and ease the burden of site management. Style-sheet language is similar to HTML code, but using CSS in conjunction with HTML means that the work of document structure and layout presentation falls to the style sheet, not the markup language. Designers control font size, spacing, background color, and text and image placement. At each organizational level of a site, authors and designers can incorporate only the new hierarchical elements needed because the parent attributes are automatically imported to the style sheet. This organized structure enables access technologies to present Web pages logically to vision-impaired users.
Testing is an integral part of site development and design.
For sight-impaired users, special browsers and screen readers function most effectively when the underlying HTML code is uncluttered and contains no errors. These automated services check for accessibility, alert you to possible coding errors, and, in some cases, suggest fixes or even fix the problem for you. But while validation services can be very handy for checking code, they're certainly not foolproof. The ideal approach is to actively test designs, using the same software used by the visually impaired. The guidelines include comprehensive explanations of accessibility issues, why certain pages are inaccessible, and detailed guidance and checklists for making improvements.