Fixed AND floating sidebar at the same time

Hello!

How can I make the sidebar fixed as well as floating?

Its easy to make it fixed using this code: position: fixed;

But the it gets fixed such that it doesn't scroll down below the browser.. right?

I want to achieve something similar to the sidebars in here: http://9gag.com/

They scroll till the end of the sidebar and then gets fixed..

Is there any way i can do that in Atahualpa?!

Thanks!