if (document.getElementById) { window.onload = swap };
function swap() {
var numimages=2;
rndimg = new Array("http://www.residentevil.ir/themes/residentevil/images/custom/banner1.jpg", "http://www.residentevil.ir/themes/residentevil/images/custom/banner2.jpg"); 
x=(Math.floor(Math.random()*numimages));
randomimage=(rndimg[x]);
document.getElementById("bnr").style.backgroundImage = "url("+ randomimage +")"; 
}