Problems with positioning in twenty eleven

Hello!

I have for some time been working on a web page, http://www.zilloman.com
I’m using the twenty eleven theme , which I have modified. The problem is that everything loses its position when I decrease the webbrowser window. It’s the same problem when you look at the site on iPad or your mobile phone. Every box loses it’s position.

Any suggestions of what is wrong with the positioning?

Very grateful for all help and advices!

Jonathan