* 'Intellectual' indexes, where individual web sites are classified by hand according to various classificatory schemes. Usually, such indices only provide the title, URL and perhaps a brief description of each site indexed. Yahoo!http://www.yahoo.com/] is a well known example of a general intellectual index of the web (ie one which is not law-specific).
* `Robot' / automated indexes, where a program (variously called a `web robot' or `web spider') traverses the web, downloading every page it encounters, so that every word on every page can be indexed by a remotely located search engine. When the search engine displays a URL as a result of a search, that URL is to the original site, not to a mirror on the remote site. Alta Vista is perhaps the best known general example of such an `internet-wide' search engine that searches an index created by a web spider. The principle advantage of this approach that it is possible to search every word that has been indexed, not just the titles and brief summary of what is on the site.
 `Universal Resource Locator' or internet address of a web page