My background looks odd

I hope someone can help me. I have reviewed all my pages and I can’t seem to find where the problem is. The past 2 weeks my blog looks as if the background is broken or displaced unless I make my browser exactly the same size as my blog. I thought it’s a matter of resizing a column but I can’t find which.

You can see it here: https://www.justjo.com/blog

I thought the problem was just with IE but I installed FF and it looks the same. I would really appreciate any help I can get with this.