Error Handling

In Codeigniter 3.X you have extra folder in views called "errors", you can all type of errors view from there to make it user friendly

Thanks. But I know about these folders too!

I mean, for 404 error page, I could create a controller and a method, and route to this method via $route['404_override']. In this way, I could have a page like other pages, with their theme, but for errors. How could these about general errors?