Over the years the humble 404 page has managed to gain status beyond that of a mere technical error page, finding its way onto t-shirts and, yes, enjoying viral status, too, like Toward’s Goat.
‘404’ is the response code that corresponds to the “Page not found” error, which is displayed whenever a website visitor tries to access a page that doesn’t exist. There are other response codes and errors, such as 403 (Forbidden), 500 (Internal Server Error), 503 (Service Unavailable), and so on. You can find a complete list here.