I've just constructed a vertical button-set with submenus to go into a menu frame on the left-hand side of the screen (a common, almost traditional, place for a menu). Unfortunately, when the submenus open they are constrained to the menu frame, cover the other buttons and wrap around. Some of the submenu items are designed to get bolder as the mouse hovers over them and, because the submenus are constrained within the menu frame and bolder text is longer, this action causes the wrap-around to change the position and layout of the submenus.
The submenus should open 'above' all frames.
I'm using IE7 and haven't yet tried this with Firefox but another poster's experience with FF suggests this may be an IE failure.