The Wayback Machine is a Web site that enables anyone to see what a particular Web site looked like at some time in the past - from 1996 to the present. This enormous archive of the Web's past requires over 100 terabytes of storage and contains 10 billion Web pages! The archive of pages was originally gathered by the owners of the Alexa program, a toolbar you can install on your PC that provides Web site information and ratings.
At the Wayback Machine site, you can search for and link to any of your favorite Web sites of the past and find them preserved very much as they were at various "snapshots" in time. For example, you can see how whatis.com looked in late 1996 and also at various times during 1997 and all the way to the present. (Occasionally, an ad that was served from another site will be missing and we noticed a few graphic images missing from our original site.) In general, however, the range and completeness of the archive is remarkable.
The Wayback Machine also carries a few "special collection" features that show how Web sites responded to the tragedy on September 11, 2001; Web pages from the U.S. election of 2000; and a "Web Pioneers" collection, that features some sites that were important to the early Internet.
The Wayback Machine is at http://web.archive.org. From time to time, the site's performance may be a bit slow.