Learn English – “Unavailable” vs. “not available”

It depends how literally you want to take it. Strictly speaking, as the address is to a specific page (info.html), you could say that it was just that page.

However, it is reasonable to assume that if the information linked to from within that page is relevant then it might apply in the original sentence, especially if that information is still on the same overall site.

Grammatically they are interchangeable. The very definition of "unavailable" is "not available". However, my gut tells me something else. When I see 'unavailable' it immediately connotes that it's a temporary condition:

The senator was unavailable for comment. He may be available later.

The web page was unavailable all afternoon. But then it came back online.

Whereas when I see 'not available' it implies to me that it's a stronger or more permanent situation. Maybe because of the emphasized not?

This service is not available in New York. And it's not likely to be any time soon.

The web page is not available outside the company. Because it's private.

While you could legitimately substitute "not available" for "unavailable" in those examples (and vice-versa), I wouldn't.