The reader email you posted that mentions webdev in straight html is dead-on, specifically noting how buttons cannot be used because screen readers cannot interpret them. For more information on this specific situation you need to familiarize yourself with Section 508: http://www.section508.gov/
Basically it is a 1998 law that requires all web information be accessible by all people (I'm paraphrasing, of course). Because it was written before many gov agencies even had web presences it is terribly outdated. It also terrifies web developers and keeps sites looking plain and worthless. Talented web developers avoid gov work as a result, and IT pros who haven't updated their skill sets in over a decade have permanent job security.
s for agencies to work on, but something that must be covered by A RULE. You cannot trust the Social Security Administration to care whether disabled people have access, so you have to mandate it. And if that clumsily drawn mandate cuts off ten other features that would help people access social security information, well . . . DIDN'T YOU SEE THERE'S A RULE????!!!
This article available online at: