Greg R. Notess updated his guide, Finding Old Web Pages: "The Web changes constantly, and sometimes that page that had just the information you needed yesterday (or last month or two years ago) is not available today. At other times you may want to see how a page's content or design has changed. There are several sources for finding Web pages as they used to exist. While Google's cache is probably the best known, the others are important alternatives that may have pages not available at Google or the Wayback Machine plus they may have an archived page from a different date. The table below notes the name of the service, the way to find the archived page, and some notes that should give some idea as to how old a page the archive may contain."