Header margins

I’d like to place the website logo starting from the top of the site, and place the navigation bar right after the logo. But there are nasty borders on top and bottom of the logo. I’d like to know how to remove them, I’ve been searching the right place for hours…

Here is a screenshot, I’d like to remove the green area: http://i307.photobucket.com/albums/nn302/ginkku2/greeena.png
My site: http://genkku.viuhka.fi

Please forgive my grammar errors, English isn’t my native.