function zeigeFenster( pfad ){
	var x = (screen.width - 650)/2;
	var y = (screen.height - 500)/2 - 32;
	if (y < 0){ y == 0; }
	var fenster = window.open(pfad, "popup", "width=650,height=500,locationbar=no,scrollbars=no,left=" + x + ",top=" + y);
}