The Internet Does Not Have Everything
Everyone needs to know that the World Wide Web (a subset of the Internet; see Internet for a definition of "Internet") is a tool, not the be-all and end-all of research. Many students begin their research assignments with the "fact" from their teachers that they'll be able to find, from now on, everything they need on the Web. Not true.
Students do need to be made aware that the Web is a great resource when you need some very current information--today's Dow Jones average, currency exchange rates, score in your favorite baseball team's game, news headlines, etc. Furthermore, through libraries there are increasing numbers of indexes that before were available on CD-ROM or in printed books, that are now accessed via the Web (only to authorized users); these are not "on" the Web per se. The term used to differentiate these proprietary and other directly inaccessible sources is the "invisible Web." The invisible Web is much larger than the visible Web.
However, some students seem to think that they can find EVERYTHING on the Web. They can't. They probably never will in their lifetimes either. There is simply too much information out there to have it all transferred to an electronic--and widely accessible--format.
Other issues that keep things from existing on the Web:
Costs can be astronomical--and who is going to pay them?
Scanning in images is expensive and time consuming (think of the millions of photographs in archives around the world),
Copyright concerns play a major role in keeping things from being widely accessible; companies want to make a profit (there are hundreds of databases that can only be used by authorized users, so they are not available "on the Web"),
Governments don't want to publicly display all of the information they have for security reasons and/or censorship purposes (most countries don't have a "Freedom of Information Act"--and even the United States of America, with this act, is selective about what is made widely available), and
Private companies have trade secrets, so they want to restrict information that they make available to the public.
The following sources are examples of items not on the Web: