Yahoo is an example of a directory. These are sites that have been reviewed or rated. Instead, a user must consciously choose to see the reviews. AltaVista is consistently one of the largest search engines on the web, in terms of pages indexed. Its comprehensive coverage and wide range of power searching commands makes it a particular favorite among researchers.
Advertisers can also pay to be listed higher within the service.
AltaVista opened in December 1995. It was owned by Digital, and now is run by Compaq, which purchased Digital in 1998. If it fails to find a match within its own database, then it will provide matching web pages from various search engines. The service went into beta in mid-April 1997 and opened fully on June 1, 1997. Results from Ask Jeeves also appear within AltaVista.