For the discussion about Wikipedia, see Wikipedia is not a link farm.

On the World Wide Web

World Wide Web

The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...

, a link farm is any group of web sites that all hyperlink

Hyperlink

In computing, a hyperlink is a reference to data that the reader can directly follow, or that is followed automatically. A hyperlink points to a whole document or to a specific element within a document. Hypertext is text with hyperlinks...

 to every other site in the group. Although some link farms can be created by hand, most are created through automated programs and services. A link farm is a form of spamming the index of a search engine

Search engine

A search engine is an information retrieval system designed to help find information stored on a computer system. The search results are usually presented in a list and are commonly called hits. Search engines help to minimize the time required to find information and the amount of information...

 (sometimes called spamdexing

Spamdexing

In computing, spamdexing is the deliberate manipulation of search engine indexes...

 or spamexing). Other link exchange systems are designed to allow individual websites to selectively exchange links with other relevant websites and are not considered a form of spamdexing

Spamdexing

In computing, spamdexing is the deliberate manipulation of search engine indexes...

.

Search engines require ways to confirm page relevancy. A known method is to examine for one-way links coming directly from relevant websites. The process of building links should not be confused with being listed on link farms, as the latter requires reciprocal return links, which often renders the overall backlink advantage useless. This is due to oscillation, causing confusion over which is the vendor site and which is the promoting site.

History

Link farms were developed by search engine optimizers

Search engine optimization

Search engine optimization is the process of improving the visibility of a website or a web page in search engines via the "natural" or un-paid search results...

 in 1999 to take advantage of the Inktomi

Inktomi

Inktomi Corporation was a California company that provided software for Internet service providers. It was founded in 1996 by UC Berkeley professor Eric Brewer and graduate student Paul Gauthier. The company was initially founded based on the real-world success of the search engine they developed...

 search engine's dependence upon link popularity. Although link popularity is used by some search engines to help establish a ranking order for search results, the Inktomi engine at the time maintained two indexes. Search results were produced from the primary index which was limited to approximately 100 million listings. Pages with few inbound links fell out of the Inktomi index on a monthly basis.

Inktomi was targeted for manipulation through link farms because it was then used by several independent but popular search engines. Yahoo!

Yahoo!

Yahoo! Inc. is an American multinational internet corporation headquartered in Sunnyvale, California, United States. The company is perhaps best known for its web portal, search engine , Yahoo! Directory, Yahoo! Mail, Yahoo! News, Yahoo! Groups, Yahoo! Answers, advertising, online mapping ,...

, then the most popular search service, also used Inktomi results to supplement its directory search feature. The link farms helped stabilize listings primarily for online business Web sites that had few natural links from larger, more stable sites in the Inktomi index.

Link farm exchanges were at first handled on an informal basis, but several service companies were founded to provide automated registration, categorization, and link page updates to member Web sites.

When the Google

Google

Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...

 search engine became popular, search engine optimizers learned that Google's ranking algorithm depended in part on a link weighting scheme called PageRank

PageRank

PageRank is a link analysis algorithm, named after Larry Page and used by the Google Internet search engine, that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web, with the purpose of "measuring" its relative importance within the set...

. Rather than simply count all inbound links equally, the PageRank

PageRank

PageRank is a link analysis algorithm, named after Larry Page and used by the Google Internet search engine, that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web, with the purpose of "measuring" its relative importance within the set...

 algorithm determines that some links may be more valuable than others, and therefore assigns them more weight than others. Link farming was adapted to help increase the PageRank of member pages.

However, the link farms became susceptible to manipulation by unscrupulous webmasters who joined the services, received inbound linkage, and then found ways to hide their outbound links or to avoid posting any links on their sites at all. Link farm managers had to implement quality controls and monitor member compliance with their rules to ensure fairness.

Alternative link farm products emerged, particularly link-finding software that identified potential reciprocal link partners, sent them template-based emails offering to exchange links, and created directory-like link pages for Web sites, in the hope of building their link popularity and PageRank.

Search engines countered the link farm movement by identifying specific attributes associated with link farm pages and filtering those pages from indexing and search results. In some cases, entire domains were removed from the search engine indexes in order to prevent them from influencing search results.

See also

• 302 Google Jacking
• Cloaking
  Cloaking
  Cloaking is a search engine optimization technique in which the content presented to the search engine spider is different from that presented to the user's browser. This is done by delivering content based on the IP addresses or the User-Agent HTTP header of the user requesting the page...
  
  
• Doorway pages
• Keyword stuffing
  Keyword stuffing
  Keyword stuffing is considered to be an unethical search engine optimization technique. Keyword stuffing occurs when a web page is loaded with keywords in the meta tags or in content...
  
  
• Methods of website linking
  Methods of website linking
  This article pertains to methods of hyperlinking to/of different websites, often used in regard to search engine optimization . Many techniques and special terminology about linking are described below.-Reciprocal link:...
  
  
• Scraper site
  Scraper site
  A scraper site is a spam website that copies all of its content from other websites using web scraping.In the last few years scraper sites have proliferated at an amazing rate for spamming search engines...
  
  
• Server farm
  Server farm
  A server farm or server cluster is a collection of computer servers usually maintained by an enterprise to accomplish server needs far beyond the capability of one machine. Server farms often have backup servers, which can take over the function of primary servers in the event of a primary server...
  
  
• Spam in blogs
  Spam in blogs
  Spam in blogs is a form of spamdexing. It is done by automatically posting random comments or promoting commercial services to blogs, wikis, guestbooks, or other publicly...
  
  
• Strongly connected component
  Strongly connected component
  A directed graph is called strongly connected if there is a path from each vertex in the graph to every other vertex. In particular, this means paths in each direction; a path from a to b and also a path from b to a....
  
  
• Web guide

External links

• Google Information for Webmasters
• Yahoo!'s Search Content Quality Guidelines
• MSN Guidelines for Successful Indexing
• The Dirty Little Secrets of Search at The New York Times
  The New York Times
  The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...