[WiseWeasel]

Ideally, either your drop-down menu responds to clicks rather than hovers, in which case it works for both mouse and touch-based devices, or it works with both hover and clicks, with clicks setting the state in a more permanent manner, even when you stop hovering. In both these ideal cases, I believe you'll need javascript in addition to your CSS. I consider hover-only menus, which disappear when you stop hovering, to be a pain to use in any case.