I'd like to know this myself too

But this seems to be rather difficult: if appended dynamically how will the system know what to do, and a menu like Drop_Down_dyn with a very deep structure will end up with hundreds of
Access Keys, while more than 10 will be a p.i.t.a. to remember (or they have to be appended to the first level only, for example).
But right now you can apply some to the main spots in your site quickly (Navi, Content, Sitemap, Subnavi, Contact...), and remember -to prevent frustration- that the internet per se can't be barrier free at all!
