Before trying to fix the CSS for the issues you apparently have, it will be a good idea to check for errors in the HTML, and eliminate potential causes there. W3C’s validator finds quite a few.
I would also like to point out that you are using a
nav element which is perfectly fine, but now you should change the doctype on top of the document to HTML5:
<!doctype html> . And then you want to get rid of the
font -tags. …
But why the iFrame?