Twenty Eleven menu system to other theme?

Hoping someone can help me out with this:

I have a Press75 “VideoFlick” theme running on this site: https://www.psychetruth.net

We wanted to alter the theme to include a custom dropdown menu below the logo.

So I copied the twenty eleven theme code and CSS for the menu because I liked the look of that one.

It works in Firefox, Chrome, IE9, but not IE8 or 7. It just displays as a list as if the CSS is ignored. And for the life of me I can’t see why not.

Is anyone good with CSS or knows if maybe I didn’t include everything I needed?

Thanks for the help.