Another little tutorial I wrote.

Making a scroll-dependent menu bar with CSS3 and JavaScript

In this tutorial I explain how to create a menu bar that can listen for scroll events and change styles once it leaves the screen.
You could use it to make your menu bar stick to the top of the screen, make the menu items appear different, make the menu bar semi-transparent, ...

You can do pretty much anything you want with it!

The knowledge gained from the tutorial is of course also applicable to elements other than a menu bar!