tabindexI just read a post from Joe Clark on accessibility articles and I think he might have misunderstood the part about tabindex. As of HTML 5, and already the defacto standard being implemented by at least Mozilla and Internet Explorer, the tabindex attribute will apply to every element in the http://www.w3.org/1999/xhtml namespace. (It will also apply to the same elements in text/html which are from an author point of view not in a namespace.) You can read on mozilla.org how tabindex should work as of Firefox 1.5. tabindex="0" is the default value and implies that the element is taken into the tabbing order. A value higher than 0 will do the same thing plus the element will get preference over elements with a lower value. A negative value will take the element out of the tabbing order, but you can still use the focus() and blur() methods on that element. Also, each element now has the tabIndex DOM attribute.
This is especially useful when certain triggers are specified on elements that are not normally focusable, such as a span element. The HTML 5 work on this can be found here.