function randomBg() {
rightimg=getrightimg();

 n = Math.floor(Math.random()*rightimg.length);
 document.getElementById('rightRandom').style.backgroundImage = rightimg[n];
}

if(window.addEventListener) {
 window.addEventListener("load", randomBg, false);
}
else if(window.attachEvent) {
 window.attachEvent("onload", randomBg);
}