function PopUp(w,h,ziel) {
        h = h - 20; var x=0, y=0, parameter="";
        if (w < screen.availWidth || h < screen.availHeight) {
          x = (screen.availWidth - w - 12) / 2;
          y = (screen.availHeight - h - 104) / 2;
          if (window.opera) y = 0; // Opera positioniert unter den Symbolleisten
          if (x<0 || y<0) { x=0; y=0; }
          else parameter = "width=" + w + ",height=" + h + ",";
        }
        parameter += "left=" + x + ",top=" + y;
        parameter += ",menubar=no,location=no,toolbar=no,status=no";
        parameter += ",resizable=no,scrollbars=no";
        var Fenster = window.open(ziel,"PopUp",parameter);
        if (Fenster) Fenster.focus();
  	return !Fenster;
  }