Sidebar appearing below posts

Okay, so I added Google Adsense to my blog today and aligned them. Then all of a sudden, after attempting and fixing the problem of aligning the skyscraper banners to the sidebar, it started appearing below the posts. So I removed all adsense (widgets), and then tried. Still messed up. I rolled back the CSS stylesheet to a previous one. Still broken.

There are W3C errors, but those aren’t the problem, I had those before I added adsense, etc. and the site worked fine.

But the sidebar is still messed up!! can someone help?! I know it’s not a post, as it was working fine an hour ago and I didn’t post any new posts nor did I edit content. Any suggestions?!