your styles look like a total mess. it's really hard to tell what's the final style that is being applied to an element as you have quite a few of them in the chain.
Why dont you use some of the available freely CSS navigations and adapt it to how you want it to work
20 Of The Best CSS Navigation Menu Techniques | Social CMS Buzz
Top 71 CSS Menus Navigation Tabs : Web Developer Lists : eConsultant
30 Exceptional CSS Navigation Techniques
there're hundreds more around if you want ;)