// JavaScript Document
if (document.getElementById) { window.onload = swap };
function swap() {
var numimages=5;
rndimg = new Array("images/mouse_17.jpg", "images/apple_17.jpg", "images/bulb_17.jpg", "images/mouse_17.jpg", "images/pencils_17.jpg"); 
x=(Math.floor(Math.random()*numimages));
randomimage=(rndimg[x]);
document.getElementById("bannerImg").style.backgroundImage = "url("+ randomimage +")"; 
}