Main menu does not look good

Hello everyone,

I have a question about my main menu. It doesn’t look good, on the left side its a few pixels higher. I can’t explain well but if you look at the menu, you’ll soon find out what’s wrong. Under the categories Maligne bolesti, Liječenje i Onkološki bolesnik is a thin line and under categories Aktivnosti, Novosti i Forum there is no line. It has something to do with sidebar ad, but I don’t know how to fix it.

A link to my site: http://www.tumor.me

Thank you very much! 🙂