Missing Method in AdvertisementsController

Error: The action app is not defined in controller AdvertisementsController

Error: Create AdvertisementsController::app() in file: app/controllers/advertisements_controller.php.

<?php
class AdvertisementsController extends AppController {

	var $name = 'Advertisements';


	function app() {

	}

}
?>

Notice: If you want to customize this error message, create app/views/errors/missing_action.ctp.