Creating custom 404 and error pages has changed in Orchard CMS. Prior to Orchard 1.4 we had to modify our web.config files to allow custom errors and then modify the handlers a bit to get Orchard to actually serve our custom pages. Now all we need to do is override a couple of shapes, NotFound.cshtml and ErrorPage.cshtml, and we have custom 404 and error pages in Orchard in seconds. In fact, my custom 404 Error page in Orchard teaches you just that!
If you read through my blog you will find it filled with Orchard Tutorials and ASP.NET MVC Tutorials. It only makes sense that my custom error page for this website is... you guessed it, a tutorial! My custom 404 Error Page teaches you how to override a couple of shapes in Orchard to create both custom 404 pages and error pages.
Below is a snapshot of the page. Go to my 404 Page and learn how to create your own!