function popup(url, w, h, nom) 
{
  var nom;
  var params = "toolbar=no,menubar=no,location=no,status=no,scrollbars=yes,resizable=no";
  if (nom)
    fenetre = nom;
  else
    fenetre = "popup";
  if (w && h)
    params += ",width="+w+",height="+h;
  else
    params += ",width=740,height=450";
  window.open( url, fenetre, params );
}