The Internet Archive is probably the most important site that most people have never heard of, much less used. It is an amazing thing: not just a huge collection of freely-available digitized materials, but a backup copy of much of today‘s Web, available through something known as the Wayback Machine. It gets its name from the fact that it lets visitors view snapshots of vast numbers of Web pages as they have changed over the last two decades since the Internet Archive was founded — some 279 billion pages currently. That feature makes it an indispensable — and generally unique — record of pages and information that have since disappeared, sometimes because somebody powerful found them inconvenient.