How do I change the size of a menu item


I build this site, and I am trying to make the (orange) color of the active menu item go over the WHOLE HIGHT of the Header, not just half.... (

I am not very experienced with CSS, although I am trying a lot lately... :wink:
BUT I couldn't find a solution...

Can I post such kind of questions here ?
(just signed up at WPMU...)

Thanx for your answer!

Cheers from Italy