Default page for 400 Bad Request responses.
Default page for 500 Internal Server Error responses, in development mode.
Default page for 404 Not Found responses, in development mode.
Default page for 500 Internal Server Error responses, in production mode.
Default page for 404 Not Found responses, in production mode.
Default page for 501 Not Implemented responses.
Default page for 401 Not Authorized responses.
Contains default error, 404, forbidden, etc. pages.