This site uses some popout CSS menus inspired by Eric Meyer's site: only CSS are used (no Javascript).
About the accessibility, the browsers that do not support the CSS, like Lynx, will display these menus as lists (no problem). With some browsers supporting a part of the CSS, these menus will not work; but the corresponding data will still be accessible in another way. There can also be display problems because of bugs in browsers (including Mozilla); however, these problems should be relatively minor.
If you are interested in the CSS code in question, it is the file screen.css.