var fenster=window.open();
if (fenster && !fenster.closed) {
        fenster.close();
        } 

  var fenster;
      function Fenster(url,width,height) {
        if (fenster && !fenster.closed) {

          fenster.close();
        } 

fenster=window.open(url, 'popup', 'top=10,left=10,width='+width+',height='+height+',left=0,top=0,scrollbars');
//fenster.focus();
      }




  function schliessen() {
        if (fenster && !fenster.closed) {
          fenster.close();
        }
      }

window.onunload = function() {
schliessen();
}

////Ende Fenster oeffnen
    //--></script>