I'm guessing by the explosion of this thread that it's affecting EVERY iOS device. Haha, chaos - good work apple. Now my email is getting spammed by all the "response to the thread" emails. I expect this to be on the tech news tomorrow... I'm off to bed anyway.
It's not your router. Just confirmed another posters suspicion / claim that it's an Apple server issue by tethering my iPad to my iPhone 4S's 4G data connection via WiFi. It does the exact same thing - which is to throw a "page not found" error.