It should work in all kind of browsers with all it's version. Not like working in IE 5.5 and not in IE 7.0.
Working in Windows 2000 in IE 6.0, but not in XP IE 6.0/IE 7.0.
Shortly I am looking for the menu which should not have any compatability issues due to browsers (IE, firefox) and OS (Windows 2000, XP, MAC..)
Whenever the new version is coming out it's diffcult to fix the issues..