This example illustrates jsDomenu set up to:
Do not confuse absolute menus with fixed menus. An absolute menu will move together with the page when you scroll. If you scroll up/down enough, it will be totally out of view. On the other hand, a fixed menu will not move with the page when you scroll. It will always be visible regardless of how much you scroll (provided it is positioned within the window when the page loads).
Check out the configuration file ("ddconfig3.js") to see how this is set up, and view the source of this page to see the necessary codes to insert on your page.
Obviously, be sure to also check out the other folders outside of "dynamicdrive" for comprehensive documentation and demos as provided by the author himself.
Enjoy!
Example prepared by Dynamic Drive