Perhaps all you are really looking for is SSI, Server Side Includes.

You can easily place your header, footer, menu or any content or code that you want to include on multiple pages.

You could have a text file for each bit of content/code to include.
Then include that file where ever you like by placing something like
<!--#include virtual="navigation.txt"--> into your html.

Change that file and it changes on all your pages. For most servers the page extension must be .shtml