Martin Kliehm has written a brief article at A List Apart where he takes a closer look at the Accessible Web 2.0 Applications with WAI-ARIA. Based on one of the most recent W3 family member Accessible Rich Internet Applications (WAI-ARIA) Suite Overview, Martin dives in to the the nest of role attributes as well as some of the states and properties W3 has been suggesting as the new accessibility drafts for web applications.

Roles are simply added as attributes into certain HTML tags, and they are already supported in FF1.5+. As far as I can see, roles makes a lot of sence just looking at the HTML. We are getting used to using tags like <ul> for navigation and other link lists, but how can a user agent tell the difference without proper markup? Main navigation lists are crucial parts of a document, and it deserves proper definitions. Roles gives us just that, and since it’s an attribute, it will not affect the rendering in “regular” browsers.

In other words: get used to adding some roles to your markup already now. It can’t hurt and it will most probably be a standard rule for the future.