Gap under Header

Im have SO much trouble trying to figure out how to get rid of the GAP under the menu header (right above your first post).

I have tried looking everywhere in the code to try and find how to get rid of it and have NO GAP, but I just can’t seem to figure it out.

Im only a beginner using WordPress and CSS, so Im still fiddling around in the dark…so when replying please be as basic as you can.

Thanks

PS I can’t give you a link to my site as its not live yet, but heres a link to the demo of the theme, where you can still see the gap under the main menu; http://webtuts.pl/test/story/