captive.apple on android mtn?

[3dartist]

My data ran out on my mtn contract. Pop up notification 'sign in to network' appear below:
http:// captive.apple.com.generate_2 (and so forth, all I could see)

From that screen it then takes me to mtn site that notifies data etc is depleted.

I have an android Sony and wondering what this sign-in means? Anything suspicious?

My Wi-Fi on phone was not turned on either.


Thanks