css primary links

Hi folks,

I have built a site for a ngo. It is still on the testserver. You can view it at http://www.einstern.eu

Somehow styling the links does not work and it seems as if I am at the end of my tether.

I am referring to the sublinks of primary links as can seen on the testsite. Klick on About in the horizontal menu at the top of the page. Then a link called Organs appears. I need to style this link, i.e. add some padding and background. But I have no idea which code to use.

Here's the html: