Floating Image
 

On a forum I was visiting, they had an image that stayed at the bottom of the screen regardless of scrolling, etc. It was not part of the background. When clicked, the image led you to a forum page.
I was looking at the code and found this:

<div class="angular_advertisement angadver_bottom angadver_left"><a target="_blank" href="linking url"><img border="0" alt="alt text" src="image url" /></a></div>

I am wondering if I want to add something similar to my site, where do I place it?