the balance of the header looks a bit strange. Although the space from the edge to the header and the header to the nav is the same, the left/right margins also the same sit on the same div as the bottom, but not the top. I think you need to either add to the top within that div, or fill it all the way with the image.
the content should not be fully justified and it needs some line-height. the line itself is too long. (18 words)
whilst it is balanced symmetrically, I dont see the connection with the different sizes, padding/margins. a proportional grid will help to tie all the elements together, and i'd try and work with the left rather than centre for the layout (although the wrapper can still be centred)
the footer also feels like an afterthought. why did you decide to cut it off like that? ONLY realised that one existed when I wondered why there was a scrollbar...
code looks pretty tidy. however as you are using html5 doctype wondering why you haven't decided to utilise some new elements, ie nav header, footer etc...
