Misalignment of columns in IE but not Firefox

In a three-column template, the content and right-column dive to the bottom of the page. I’ve tried everything I know how to do – print and examine code, systematically delete sidebar elements, etc. The problem occurs in IE but not Firefox. Can someone please have a look at ‘https://www.syntaxandsoul.com’ in IE and give clueless me a clue. I’m probably missing something obvious and will be real embarrased but this is one of those times when — help!