Hiding links to alternate versions so that they're only seen, e.g., by a screen reader or with plugins turned off.

This, this, so much this. Because so many people think that programming for accessibility means "programming for blind users who are using screenreaders, which of course means JAWS because that's the only one we know about", they think that making alternate versions and alternate functionality available in a way that is hidden from everyone but screenreaders is valid. I actually have to have a NaturallySpeaking macro for "toggle styles", because turning off CSS is the only way I can find those alternate versions and that alternate functionality.