var popUpWin=0;
function popUpWindow(URLStr, left, top, width, height)
{
left=(screen.availWidth - width) / 2
top = (screen.availHeight - height) / 2

  if(popUpWin)
  {
    if(!popUpWin.closed) popUpWin.close();
  }
  popUpWin = open(URLStr, 'popUpWin', 'titlebar=no,toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=no,copyhistory=no,width='+width+',height='+height+',left='+left+', top='+top+',screenX='+left+',screenY='+top+'');
}