The Internet is, by its very nature, a transitory medium-pages come and go. But if you had a publicly available Web page in the past three years, chances are that a copy of it is in the collection of the Internet Archive, a nonprofit group that saves "snapshots" of the Internet.

The Archive was founded by Brewster Kahle, whose San Francisco-based Web browser company, Alexa Internet, collects the snapshots every two months and donates the digital tapes to the Archive. As of May, the Archive was in excess of 13 terabytes (a terabyte is 1 million megabytes); in comparison, the Library of Congress holds the equivalent of about 20 terabytes. The Archive is stored in two separate machines in different locations. "It's too important to have in one place. An earthquake could cause destruction of a collection that's as large as the largest library ever built by humans," says Kahle.