Recently, and I mean 5-minutes-ago-recently, I was fixing a bug with this design concerning som floating failures. Namely, the sidebar kept jumping down below the last content <p>. After 2 hours of playing around with the WebDeveloper toolbar for firefox i found the solution: I forgot to unfloat the child elements of the sidebar. After a quick div#sidebar *{ float: none } the problem was fixed. So, take this as a warning: remember to undo your floating.