Braille is not a language. Media aren't languages. Although parameters of display are an integral part of presentation markup, they must not rule content. Universal Design concepts make this a central issue. The same considerations that would enable Helen Keller to access a text or graphical document apply to allowing Beethoven to have some experience of his own music or a Cell Phone user to get the arrival time of the next train.
Accessibility is a subset of usability.
Usability demands that any material published on the Web be Device Independent. Many arguments for Device Independence are not centered on accessibility issues, but on general usability concerns. The semantics of presentation and structure must be made clear at the primary design level. These considerations force emphasis on the semantics and not on the representation. Attend to what you mean and allow the user to extract that meaning with whatever device must be used.