function popUpInviter(name, width, height, ajax_url) {
  var dialog = new FB.UI.FBMLPopupDialog(name, "");
  dialog.setContentHeight(height);
  dialog.setContentWidth(width);

  jQuery.ajax({ type: "GET",
    url: ajax_url, 
    success: function(data) {
      dialog.setFBMLContent(data);
      dialog.show();
    }
  });
}