Regarding: http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2010-December/029559.html
This has (somewhat) been resolved: Benjamin has pointed out that aria-invalid = "spelling|grammar" would work just fine with <mark>. It's simply not implemented by vendors at the moment. It is covered
by the WAI ARIA 1.0 LC doc. somebody [mark aria-invalid="spelling"]mispeld[/mark] this text.
