Sidebar gets pushed below content

So, I got this problem everybody knows: My sidebar gets pushed below my content.

I have absolutely no clue why…

The div-body that includes content and sidebar has a width of 880px, #content is 500px, #sidebar 250px

I already tried varying widths but no matter what, the sidebar is always displayed below the content.

I also checked for missing/wrong <div>-tags but everything’s fine there, in the template-files as well as in the posts.

I’m using the Starkers theme to design my own theme but the mistake can’t lie there because I used exactly the same files for several other themes already without encountering any trouble.

Also there are no images or anything that too big and thus pushing anything away…

I’m at a loss here and would really appreciate some help! ??