When iOS attaches to a WiFi network, it checks to see if that network requires additional credentials by attempting to access this file on Apple's website. If it sees the file, iOS knows it has Internet connectivity and it will remember that WiFi network. If it can't see the file, iOS assumes that the network requires some additional form of authentication (like a user name and password, or a WiFi access code).
This is fine, but things kind of fell down yesterday. The success.html file was missing or otherwise unavailable; if you tried to hit its URL directly with a Web browser, you were redirected to Apple's generic "Page not found" 404 error page
I can't remember clearly. Have Apple's launches always been this way, or were they more polished several years ago?