var pre = new Image();
pre.src = "images/promo/promo_buy0.jpg";
pre.src = "images/promo/promo_buy1.jpg";
pre.src = "images/promo/promo_listen0.jpg";
pre.src = "images/promo/promo_listen1.jpg";
pre.src = "images/promo/watch_video_promo0.gif";
pre.src = "images/promo/watch_video_promo1.gif";

function promoHover(ev) {
	var evt = ev ? ev : event; 
   	var el = evt.target ? evt.target : evt.srcElement;	
   	//alert(el.id);
   	var ext = (el.id == "watch_video_promo") ? "gif" : "jpg";
   	   	
   	if (evt.type.toLowerCase() == "mouseover") {
   		el.src = "images/promo/" + el.id + "1." + ext;
   	} else {
		el.src = "images/promo/" + el.id + "0." + ext;
	}
   	
}