Here's a nice top ten of things not to do when building accessible sites:

1. Don't use verbose ALT text. ALT text for information-based images should be short and succinct. Decorative images should never have ALT text.

2. Don't use random characters, such as vertical bars, to separate links

3. Don't insert text into form fields

4. Don't use access keys as they can override keyboard shortcuts for screen readers

5. Don't use table summaries (unless there isn't sufficient information provided about the table on the page)

6. Don't forget content organisation. Structure text properly with short paragraphs, headings, lists and plain and simple language.

7. Don't worry too much about writing accessibility help pages since they won't really be read

8. Don't agonise over acronyms and abbreviations

9. Don't change the tab order (unless you have a very good reason)

10. Don't forget to listen with a screen reader

Links:

• 10 common errors when implementing accessibility 

Henrik Olsen - April 07, 2008 - via Usability In the News