This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
Here is the function I am using
var myBanners=new Array(3);
var i = Math.floor(Math.random() * 3);