Problem with theme in Internet Explorer

Hi!

I have a problem with the template on my website;

As you can see it looks just fine in Firefox, https://affiliatecoachen.se

But when i look at it in Internet Explorer, it looks quite strange as you can see, and the menu has been “pushed down” below the front-page posts. However, i only have this problem when i look at the site′s index. When i look at a subpage everything seems to be just fine.

Does anyone have a suggestion of what may cause this problem?

Thanks for helping
Christopher