function showAd(ad) {
    obj = document.getElementById("ad_" + ad);
    bgObj = document.getElementById("bg_" + ad);
	
    bgObj.style.width = obj.style.width;
    bgObj.style.height = obj.style.height;
		
    offsetX = 0;
    offsetY = 0;
			
    while (obj.nodeName != "BODY") {
		
        offsetX += obj.offsetLeft;
        offsetY += obj.offsetTop;
		//alert( obj.nodeName +" "+ offsetX +" "+ offsetY)
        obj = obj.offsetParent;
    }
	
    bgObj.style.left = offsetX+"px";
    bgObj.style.top = offsetY+"px";
    bgObj.style.display = "";
}