var meinFenster;
      var position1
      var position2
        function pop(datei)
        {
        position2=(screen.availHeight/2);
        position1==(screen.availWidth/2);
meinFenster=window.open(datei,"f","width=600,height=600,left=100,top=60,menuebar=no,scrollbar=no,status=no,location=no,resizable=no,toolbar=no, titelbar=no,"); 
        meinFenster.focus();
        }
        function fenster_zu()
        {
        if(meinFenster && !meinFenster.closed)
        {
        meinFenster.close();
        }
        }