I know that to get the 404 page not found error page working you have to change the urlsegment to "404". However it makes no sense to me why the system will auto generate an error page during a dev/build but you have to go in and change the page to make it work. Also once you change the urlsegment, another dev/build will auto generate another page-not-found page that I have to delete each and every time.
It seems to me that since the error page is auto generated at dev/build and often with templates that are unfinished as they are in the development stage, maybe a better way could be made.
At the end of a project when a site is going to go live I always have to open up the 404.html page in assets and manually fix tons of errors and issues. I would rather have a button or an action like ?generate404=1 that will make the error page when I am ready to make it.
Of course it is possible that I am missing something important here and the way it is being done may be better than my proposed way.