I've been adding code for Who Sees Ads to this theme and nearly had a heart attack when I was checking out the ad placement on one of my pages. The sidebar dropped to beneath the page content. Thinking I had broke the theme I reinstalled a clean copy of the page template. Only it didn't fix the problem.
There was a tiny sigh of relief when I discovered that I was viewing the page in IE, and that my pages viewed okay in Firefox. Most of my readers do use FF, but other bloggers may not be so lucky.