If you are somehow involved in supporting interactive web content, please consider reviewing one or more of these W3C documents related to accessibility.
For everyone involved in web content, this is the document with actual "Last Call Working Draft" status:
Accessible Rich Internet Applications (WAI-ARIA) 1.0 - Last Call Working Draft
For web application ninjas:
WAI-ARIA Best Practices - updated Working Draft
For browser developers:
WAI-ARIA User Agent Implementation Guide - First Public Working Draft
It is important that these documents are understandable and consistent. The deadline for having an impact via your comments is April 17th, 2009. Official channel is: firstname.lastname@example.org (see this email for details).