Comment by p4bl0

This has all its place on hacker news because it is a fun hack, but it's not at all practical. Not only it doesn't work in all browsers even fairly recent ones (service workers), but even when it works it necessitates javascript enabled, and imposes a non negligible additional load time. And more importantly, with the way it is recommended to use it using 404.html file as a "catch all", it means all your pages are served as 404 errors, which can be a problem for a lot of things (starting with search engine indexing).