There's something of an oxymoron going on there in the heading. Can you spot it? The words 'accessibility' and 'AJAX'. They really are not the best of bed fellows, as many people have discovered. However, although many of us web professionals just 'kinda know' that AJAX is bad for web accessibility, when pushed many would not be able to say exactly why or how certain screen readers cope with content that's been changed using AJAX (or using DOM Scripting methods that don't make use of AJAX at all). One man who can claim to know a bit about it is James Edwards (aka Brothercake):

Over the last few months (and earlier) I've been involved in researching how the leading screen readers and other assistive devices respond to JavaScript: what kinds of events they generate or respond to, and under what circumstances. The research is based at Access Matters , and coordinated by Bob Easton, Derek Featherstone, Mike Stenhouse and myself.

In addition to that, I did a great deal of primary research for my recently published book, The JavaScript Anthology . The research was designed to find out how assistive devices respond to scripts that update the DOM periodically or asynchronously, such as the items in a scrolling news-ticker, or responses to an XMLHttpRequest.

The above is an excerpt from an article that James has published on Sitepoint entitled AJAX and Screenreaders: When Can it Work? which I strongly advise all web professionals to read and absorb. Even if you're not currently doing 'cool' things with AJAX, you should read it so that you are aware of the impact of any future development work, should you choose to go down that road. Top work, James.

This is cross-posted at webstandards.org. If you have any comments, please add them over there