Generally speaking, much of the real world has some sort of presence on the web. This
includes
Many copyrighted materials - You can find web sites for Oprah's Book
Club, but you cannot find the books themselves (although you can purchase them and have
them delivered).
With that said, there is a large amount of copyrighted information on the web. Much of
this information compliments, rather than copies, existing forms of commercial
information.
A lot of copyright-expired material, particularly literature, is available on the web.
Generally speaking, 75 years is about when most copyrights expire.
Your home (or business) computer - If you are at work, you cannot get
info off of your home computer or vice versa, using the basic Internet.
Personal or ineffable information - Generally speaking, if you can't
think of where to look in a library or bookstore or the Yellow Pages for your information,
you probably won't be able to find it on the web, either.