Marcos said "the reason we have "should" and "may" is to accommodate HTML, which is not as accessible as it could be. To have "must" would mean that HTML4.01 could not meet the requirement."
Interesting... My experience has been that HTML 4.01 can be made accessible if it is carefully coded. WCAG 2.0 has many techniques for this, including for scripted and styled content. While it is true than many (possibly most) DHTML applications have accessibility issues, I do not believe that this is the fault of the standard so much as the authors. Do you have examples of things that cannot be made accessible in HTML 4.01? Thanks again, Cynthia
