Couldn't find anything in the github documentation and also here on SO. But I was wondering if there could be a http://foo.github.com for a private repository named foo which is accessible only one had access to the foo repository itself.
I remember having read something about github pages always being public but can't seem to find that anymore.
And surprisingly, I can't seem to find anyone else asking the question either.
I had raised a support ticket against Github and got a response confirming the fact that ALL pages are public. I've now requested them to add a note to help.github.com/pages.