function dcolAd(ad_root,position) {

	if (document.layers) {
		
		switch (position) {
			case "admedia" :
				var height = "60";
				var width= "468";
				break;
			case "promotile" :
				var height = "60";
				var width= "120";
				break;
			case "tower120x600" :
				var height = "600";
				var width= "120";
				break;
			default :
				var height = "25";
				var width= "460";
				break;
		}

	var URL = "http://ads.discovery.com/RealMedia/ads/click_nx.ads/www.discovery.com/" + ad_root + "/default.html@" + position;
	var IMGSRC = "http://ads.discovery.com/RealMedia/ads/adstream_nx.ads/www.discovery.com/" + ad_root + "/default.html@" + position;

	document.write("<a href='" + URL + "' target='_blank'><img src='" + IMGSRC + "' width='" + width + "' height='" + height + "' border='0'></a>");

	} 

}