UpdatePanel & Section 508 – Microsoft AJAX Library and ASP.NET 2.0 AJAX Extensions
The new UpdatePanel supports the Section 508 standard. This is a great improvement over the previous CTP. As a result, users that access an ASP.NET application through a screen reader will be able to get the updated sections of page. Previous builds of the UpdatePanel did not work properly with screen readers. While this is a great step forward, this is not the be-all, end-all with regards to accessibility and the UpdatePanel. One question that never seems to be answered is how is a screenreader user notified that something has changed on the screen? How does a user know that a new grid with data in it is being displayed?
Originally pulled from: http://morewally.com/cs/blogs/wallym/archive/2006/10/20/431.aspx