var busyBodies = ['tabcontainer'];

Ajax.Responders.register({
  onLoading: function() {
    busyBodies.each(function(id) {
      if ($(id)) Element.addClassName(id, 'busy');
    });
  },
  onComplete: function() {
    busyBodies.each(function(id) {
      if ($(id)) Element.removeClassName(id, 'busy');
    });
  }
});