IBM's Accessibilty heuristic:  http://www-03.ibm.com/able/guidelines/web/accessweb.html

1. Provide meaninful and relevant alternatives to non-text elements

 2. Support consistient and correctly tagged navigation

 3. Allow complete and efficient keyboard usage

 4. Respect users' browser settings

 5. Ensure appropriate use of standard and proprietary controls

 6. Do not rely on colour alone to code and distinguish

 7. Allow users control of potential distractions

 
8. Allow users to understand and control time restraints