// JavaScript Document
<!-- 
if (document.getElementById) { window.onload = swap };
function swap() {
var numimages=4;
rndimg = new Array("images/BgImages/BgPic1.jpg", "images/BgImages/BgPic2.jpg", "images/BgImages/BgPic3.jpg", "images/BgImages/BgPic4.jpg"); 
x=(Math.floor(Math.random()*numimages));
randomimage=(rndimg[x]);
document.getElementById("banner").style.backgroundImage = "url("+ randomimage +")"; 
}
//-->