var pop_win=null;

function open_win(file_name)
{
  if (pop_win)
  {
    pop_win.close();
  }

  pop_win= window.open(file_name, 'photos', 'width=840, height=580, left=20, top=20' + ', scrollbars=yes,resizable=no,status=no,toolbar=no,menubar=no,titlebar=no');
  pop_win.focus();
}