function getAd(){
	var urls = new Array("images/logo0.jpg",
	"images/logo1.jpg",
	"images/logo2.jpg"
	);
	var selectedUrl = Math.round(Math.random() * (urls.length-1));
    return "<a  target=_parent href='/s4c/'><img src='"+urls[selectedUrl]+"' border=0 width=370 height=187></a>";
}document.write(getAd());