[SOLVED] header and nav bar 100%, center content 70%. How to do?

I'm looking to have the header and nav bar fill 100% of the page and then the center content take up 70% in the center of the screen.

Edit -- I figured it out.. I set the page to 100% and the post container at 70%.. works like a charm.

But now I can't get the sidebar to indent 75px. Edit - I gave up and moved on.

Now I can't get rid of the 15px padding between the nav bar and the post container.
Any help appreciated.