Ability to add multiple ads - How does this feature work?

[microrec]

Hello there,

What do I have to do on the AD Content window to make it choose between ads when the page is reloaded. I Have several different banners and I want to display a different one each time the page reloads. The banner code is something like

Code Select Expand

<a href="http://www.website.com"><img src="http://www.website.com/banner.gif"></a>

All the banners use this code. Can anybody help?