//if (document.getElementById) { window.onload = swap };
function swap() {
var numimages=5;
rndimg = new Array("images/firelands_bg.jpg", "images/firelands_bg2.jpg", "images/firelands_bg3.jpg", "images/firelands_bg4.jpg", "images/firelands_bg5.jpg"); 
x=(Math.floor(Math.random()*numimages));
randomimage=(rndimg[x]);
document.getElementById("body").style.backgroundImage = "url("+ randomimage +")"; 
}