[zeusk]

The difference is that search engines will generally redirect to the external website while archive.org lets you browse the page on their domain.

As an added exercise, maybe try translate.google.com to see if it's blocked as well.

[jolmg]

I'm sure they mean the thumbnail images you can browse in Google's domain.

[lazerl0rd]

There's SafeSearch for that, which can be enforced at the DNS level.