var winpop=0;

function winpo(url_str)
{
  if(winpop)
  {
    if(!winpop.closed) winpop.close();
  }
    winpop = open(url_str, 'winpop', 'toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=no,resizable=yes,copyhistory=yes');
}