Centering body items on front page

I really like the Sydney theme and want to use it for my website, however I am having difficulties getting the body of the front page to centre under the header.

Here is the link to my sandbox to show what I mean:

http://sandbox.thesupercargo.com

Items in the body seem to be floated to the left. I can’t seem to identify the correct piece of code that governs this. Any suggestions gratefully received.

John