If by designing your site, you mean creating the look and feel (compared to bulding the actual HTML site) in the form of a prototype, I'd recommmend removing the footer from the shared layer, converting it to a symbol, and then placing the symbol at the desired location for each page inthe mock up.
If you mean you are actually trying to build your final site in Fireworks, STOP. FW is not a web site construction tool, it's a design tool. The kind of thing you are doing, for a final web site, is best done in an HTML editor such as Dreamweaver.
You create your assets in Fireworks, optimize, export and then build your html/css in Dreamweaver, or use tools such as the CSS Properties panel (found on labs.adobe.com) to extract the CSS properties from Fireworks vectors and text, and then incorporate those declarations into your CSS.
Hope this helps.