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== Methods ==
[[File:Websites interlinking to illustrate PageRank.png|thumb|right|375px|Suppose each circle is a website, and an arrow is a link from one website to another, such that a user can click on a link within, say, website F to go to website B, but not vice versa. Search engines begin by assuming that each website has an equal chance of being chosen by a user. Next, crawlers examine which websites link to which other websites and guess that websites with more incoming links contain valuable information that users want.]]
[[File:Websites interlinking to illustrate PageRank percents.png|thumb|right|375px|Search engines uses complex mathematical algorithms to guess which websites a user seeks, based in part on examination of how websites link to each other. Since website B is the recipient of numerous inbound links, B ranks highly in a web search, and will come up early in a web search. Further, since B is popular, and has an outbound link to C, C ranks highly too.]]
=== Getting indexed ===
The leading search engines, such as [[Google]], [[Bing]] and [[Yahoo!]], use [[Web crawler|crawlers]] to find pages for their algorithmic search results. Pages that are linked from other search engine indexed pages do not need to be submitted because they are found automatically. Some search engines, notably Yahoo!, operate a paid submission service that guarantee crawling for either a set fee or [[Pay per click|cost per click]].<ref>{{cite web|url=http://searchenginewatch.com/showPage.html?page=2167871|title= Submitting To Search Crawlers: Google, Yahoo, Ask & Microsoft's Live Search |date= 2007-03-12|accessdate=2007-05-15|publisher=[[Search Engine Watch]]}}</ref> Such programs usually guarantee inclusion in the database, but do not guarantee specific ranking within the search results.{{Dead link|date=April 2010}}<ref>{{Dead link|date=April 2010}}{{cite web|title=Search Submit|url=http://searchmarketing.yahoo.com/srchsb/index.php|publisher=searchmarketing.yahoo.com|accessdate=2007-05-09}}{{dead link|date=September 2011}}</ref> Two major directories, the Yahoo Directory and the [[Open Directory Project]] both require manual submission and human editorial review.<ref>{{cite web|url=http://searchenginewatch.com/showPage.html?page=2167881|title= Submitting To Directories: Yahoo & The Open Directory |date= 2007-03-12|accessdate=2007-05-15|publisher=[[Search Engine Watch]]}}</ref> Google offers [[Google Webmaster Tools]], for which an XML [[Sitemap]] feed can be created and submitted for free to ensure that all pages are found, especially pages that aren't discoverable by automatically following links.<ref>{{cite web|url=http://www.google.com/support/webmasters/bin/answer.py?answer=40318&topic=8514|title=What is a Sitemap file and why should I have one?|publisher=google.com|accessdate=2007-03-19}}</ref>
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