109110 web coding / css? project

ok - we have the attached site coded. There are two pages. [login to view URL] and [login to view URL] for the interior pages. We need a solution so that the header(s), left menu, and footer are served across the entire website and not driven by the code on each individual page. (note -- the two pages have different headers) We need to be able to make changes in those three areas in one spot and have it reflected across the entire spot. Please post how you will provide this solution, whether it is through css, include files, or another method.