[JAVASCRIPT] Dropdown issue

[DoubleJ]

I made an xhtml/css based dropdown menu.
But now I wanted to try and fix it so it works in IE too(similar to here on phpBBstyles.com).
Now it worked nicely in IE but when I add the #navigation-box class in my stylesheet it does not work anymore.

How could I make it to work:
http://dev.doublejweb.net/issue/menu.html
http://dev.doublejweb.net/issue/style.css
the javascript is in the header of menu.html