It's a little known fact that you can easily substitute the default Rails HTML error pages with something more pleasant. You may have noticed the 404.html, 422.html and 500.html files that are generated with every new Rails project and wondered if there's a clean way to style them like the rest of your application. There is, and it's surprisingly simple.
The default status code templates are served by a Rack exception application. You can override this to be any Rack compatible app, including your applications router:
# config/application.rb
config.exceptions_app = self.routes