How does CSS opacity affect accessibility?

Question

After browsing a number of Google and other SO articles, I\'ve decided to ask my question plainly in hopes of a simple, direct answer.

To add one further step to the dis

Answer 1

opacity: 0; won't hide content from screen readers, though it'll hide content from sighted users and partially sighted users.
It's like displaying a white text on a white background (or transparent, you get the idea).
It'll be mapped to the accessibility API, you should still see the pointer changing above links, edit: you can still select text /edit, and somebody should test to see if, when tabulating links and form elements, the default dotted outline will display as usual or will be transparent. Edit: the latter, just tested with Firebug on this page.