Page content not filling screen

I’m a complete virgin to word press, and after publishing my first site, seem to be having a problem with the layout.

If you visit http://www.willbarraclough.co.uk you can see the content fills the page nicely, however, click either Profile of Contact and you can see the content sticks to the left leaving a lot of white space down the right. I can’t seem to work out how to edit this, I’ve played with the CSS files in conjunction with reading other posts, but it doesn’t seem to be working.

Any pointers?