Problem with Menu size

I got a lil problem,.... i haven't changed anything, but unfortunatelly I've got a problem now, for some reason the mneü size and fonts is different whey cou come to the page... if you've once klicked a link in the menu then it looks libe before... what can I do? the page is http://www.fantasy-cuisine.de

Red: Fault+
Blue: as it should looks like...

Hi
I've checked it on my FF and everything is ok.