Layout broken when changing size of browser windows

Hi, ive got one problem with Tank theme, When displaying on desktop zooming in/out everyting is OK, but when i move the browser windows to one site of monitor and snap it there (like in windows 7) the browser changes the size and the site become completely deformed. Bellow is a picture to dhat problem. I didnt made any big changes in the code.
Thanks for response.

[url=http://www.imagehosting.cz/?v=untitlaya.png][img]http://www.imagehosting.cz/thumbs/untitlaya.png[/img][/url]

here is the problem image link:
http://www.imagehosting.cz/images/untitlaya.png