Error pages in DD4T (404 and 500)

In DD4T the 404 page can be retrieved as below, Override the Action Page, and when the Page is null return the NotFound Action. In the NotFound action, Query the Broker for the 404  page and return the view.

The 500 Error page can be throw from the Global level as below, when error occurred handle it the global level and return just view with error information