function popup(url, name, width, height) {
      if (isNav4 || isIE4) {
        var screenPosX,screenPosY;
        screenPosX = (screen.availWidth - width) / 2;
        screenPosY = (screen.availHeight - height) / 2;
        if (isNav4 || isNav6) {
          window.open(url, name,'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,resizable=0, copyhistory=0,width='+width+',height='+height+',screenX='+screenPosX+',screenY='+screenPosY+'');
        }
        if (isIE4) {
          newwin = window.open(url, name,'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,resizable=0, copyhistory=0,width='+width+',height='+height+',left='+screenPosX+',top='+screenPosY+'');    
        }
      } else {
        window.open(url, name,'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,resizable=0, copyhistory=0,width='+width+',height='+height);
      }
    }