I spent a great deal of time over the weekend getting the menus to function well on the latest versions of both IE and Netscape. For some reason only the first item shows up in the menus on Opera, but I didn't have time to determine why. I haven't tested on older browsers yet either.
What I did do is make the buttons clickable, so with any browser you should be able to click on the button to make a menu appear on a regular HTML page in the top frame.