Ummm ... are you sure? :lol:
To get that layout shown in the image, float the inner elements left and right as appropriate. Also give overflow: hidden to the container.
So, for example, inside #header put a div like "header-inner", give it the desired width (say 1000px), and center is with margin: 0 auto; Also give it overflow: hidden;
Inside that, have the box for the left side floated left, and the box containing the boxes to the right floated right.