#Primary float left in TwentyThirteen?

Hi!

I am having trouble getting #Primary anywhere but centered on the screen. I have styled it via its div class name, .content-area, to float left and have a width of 40%. In my final design it’s supposed to be 70%, but 40% illustrates the issue better.

Here’s a link: fsdev.tew.no
I’ve tried troubleshooting myself, removing all padding and margins, yet to find something that solves this.

Any ideas? Thanks.