/*set the Header ID's background img style*/
function randHeader() {
	var myRand = Math.floor(Math.random()*4 + 1);
	myRandImg = new Image();
	myRandImg.src = '/img/main_header'+myRand+'.jpg';
	$('header').style.background = 'url('+myRandImg.src+') no-repeat top left';
}