brotherhood_of_LAN - 12:21 pm on Dec 1, 2010 (gmt 0)

There are CSS-based solutions that would likely be more search engine friendly. SE's are thought to be able to parse certain javascript but it's best to be on the safe side when it's as important as your sites main navigation.

The first result for 'css dropdown' on a search brought me this:
[tjkdesign.com...]