function popup_login(nom_de_la_page, nom_interne_de_la_fenetre,width,height) {
		pixtop = (screen.height - 120)/2;
		pixleft = (screen.width - 450)/2;
		window.open (nom_de_la_page, nom_interne_de_la_fenetre, config='height=120,width=450,toolbar=no,menubar=no,scrollbars=no,resizable=no,location=yes,directories=yes,status=no,top='+pixtop+',left='+pixleft+'');
		}