You might also want to take a look at the 'Viewable with Any Browser Campaign', found here: http://www.anybrowser.org/campaign/

Did you check the example of an accessible page from that article GG posted? This: http://ken.me.com.au/
Strange enough it claims to validate with "RDF" and "P3P", things I've never heard of but which still have something to do with W3C. Check the RDF validating, it gives a bunch of warning messages. Oops.