function popup(nom,page,hauteur,largeur)
{
var top=(screen.height-hauteur)/2;
var left=(screen.width-largeur)/2;
var proprietes="top="+top+",left="+left+",width="+largeur+",height="+hauteur+",menubar=no,scrollbars=no,statusbar=no";
var viewerpop = window.open(page,nom,proprietes);
  if (!viewerpop.opener)viewerpop.opener=self;
  if (viewerpop.focus)viewerpop.focus();
}