// JavaScript Document


function PopupCentrer(page,largeur,hauteur,options) {
  var top=(screen.height-hauteur)/2;
  var left=(screen.width-largeur)/2;
  window.open(page,"","top="+top+",left="+left+",width="+largeur+",height="+hauteur+","+options);
}

<!-- option peut etre "menubar=no,scrollbars=no,statusbar=no"-->
<!-- appel : javascript:PopupCentrer('nompage.htm',520,220,'menubar=no,scrollbars=no,statusbar=no') -->