Where does this padding come from?

Hello, I hope there is someone who can help me:
I´m using the GKTabs-Module on this page: http://testserver.grizzlyworld.de/index ... Itemid=144

I searched through all css-Files, but I can´t get rid of the padding left and top. The Maincontent has 550px width, the image in it has same width. Look at the picture and you´ll see what I mean.

I have nearly found out every piece to change alone, but this padding drives me crazy...

Thanks,
Stephanie