function popup(l,h,url,id) {
hauteur=Math.round((screen.availHeight-h)/2);
largeur=Math.round((screen.availWidth-l)/2);
window.open(url,id, "toolbar=0,location=0,directories=0,status=0, scrollbars=yes,resizable=yes,menubar=0,top="+hauteur+",left="+largeur+",width="+l+",height="+h);
}