CSS: fix a little bug and clean the HTML code

I have created a very simple web site (as per customer request). It's two pages and three sub-pages. I have included a no-table CSS and it works. You can see it here: <[login to view URL]> The background is a gradient at the edges and a white page at the center. If you click the menu item CERTIFICAZIONI and then click on one of the three logos (you will land maybe here: <[login to view URL]>), you'll see an image with a certificate; if you scroll up the page, you'll see the image to cover the menu! I want the CSS to be fixed, not to allow the certificate image to cover the menu. **Edit:** I am sorry to edit the project description, but I have receveid some comments (very much appreciated) that state the HTML have some problems (semantically incorrect) and that it is not W3C. In addition to fixing the simple scrolling problem above, I'd like to have the 2 HTML pages (and the 3 subpages) to be corrected and made fully W3C compliant and SEO friendly. Thank you for all the good answers and proposals. After your replies I will soon choose the winning bidder. ## Deliverables This is a very simple project, but even so, what I'd like to know is **how** you would fix the problem (without giving any source code) and why. I'm not interested in copy&paste bids.