In computing, spamdexing (also known as search spam, search engine spam, web spam, black hat SEO or search engine poisoning) is the deliberate manipulation of search engine indexes. It involves a number of methods, such as repeating unrelated phrases, to manipulate the relevance or prominence of resources indexed in a manner inconsistent with the purpose of the indexing system. It could be considered to be a part of Search Engine Optimization, though there are many Search Engine Optimization methods that improve the quality and appearance of the content of web sites and serve content useful to many users. Search engines use a variety of algorithms to determine relevancy ranking. Some of these include determining whether the search term appears in the body text or URL of a web page. Many search engines check for instances of spamdexing and will remove suspect pages from their indexes. Also, people working for a search-engine organization can quickly block the results-listing from entire websites that use spamdexing, perhaps alerted by user complaints of false matches. The rise of spamdexing in the mid-1990s made the leading search engines of the time less useful. Using unethical methods to make websites rank higher in search engine results than they otherwise would is commonly referred to in the SEO (Search Engine Optimization) industry as "Black Hat SEO."