function popup (url,breite,hoehe) {
	var name = navigator.appName
	if (name != "Microsoft Internet Explorer") {
	  breite*=1.3;
	  hoehe+=20;
	}
	absleft = (screen.width-breite)/2;
	abstop = (screen.height-hoehe)/2;
	param = "directories=no,menubar=no,toolbar=no,scrollbars=yes,left=" + absleft + ",top=" + abstop +",resizable=yes,width=" + breite + ",height=" + hoehe;
	popupwindow = window.open(url, "", param);
	if (!popupwindow.opener) { popupwindow.opener=self; }	
 }