There are many websites which are totally static. They can have an Ajax twist with a little touch.
In order to make it work, The website content is marked like:
<!-- begin content -->
*your primary content*
<!-- end content -->
to make the script know which is the content area to be loaded. A detailed documentation can be found here.
P.S. Thanks to Nick for the suggestion.
Requirements: No Requirements
Compatibility: All Major Browsers