Hi,
I notoced a minor problem with frames. You can see it in your frames example. When
you move a mouse over a main menu, a submenu appears in another frame. If you move the mouse out of the main menu, keeping it in the same frame (the frame where the main menu is) the submenu does not disappear from the other frame.
I tried it with NS 4.79, IE 5.5, IE 6.0.26, and NS 6.1 and the problem shows up in every one of them.