Backlink

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Backlinks (or back-links [UK]) are incoming links to a website or web page. In the search engine optimization (SEO) world, the number of backlinks is one indication of the popularity or importance of that website or page (though other measures, such as PageRank, are likely to be more important). Outside of SEO, the backlinks of a webpage may be of significant personal, cultural or semantic interest: they indicate who is paying attention to that page.

In basic link terminology, a backlink is any link received by a web node (web page, directory, website, or top level domain) from another web node (Björneborn and Ingwersen, 2004). Backlinks are also known as incoming links, inbound links, inlinks, and inward links.

Search engine rankings

Search engines often use the number of backlinks that a website has as one of the most important factors for determining that website's search engine ranking. Websites often employ various techniques (called search engine optimization, usually shortened to SEO) to increase the number of backlinks pointing to their website. Some methods are free for use by everyone whereas some methods like linkbaiting requires quite a bit of planning and marketing to work. Some websites stumble upon "linkbaiting" naturally; the sites that are the first with a tidbit of 'breaking news' about a celebrity are good examples of that. When "linkbait" happens, many websites will link to the 'baiting' website because there is information there that is of extreme interest to a large number of people.

There are several factors that determine the value of a backlink. Backlinks from authoritative sites on a given topic are highly valuable. If both sites have content geared toward the keyword topic, the backlink is considered relevant and believed to have strong influence on the search engine rankings of the webpage granted the backlink. A backlink represents a favorable 'editorial vote' for the receiving webpage from another granting webpage. Another important factor is the anchor text of the backlink. Anchor text is the descriptive labeling of the hyperlink as it appears on a webpage. Search engine bots (i.e., spiders, crawlers, etc.) examine the anchor text to evaluate how relevant it is to the content on a webpage. Anchor text and webpage content congruency are highly weighted in search engine results page (SERP) rankings of your webpage with respect to any given keyword query by a search engine user.

Obtaining backlinks from search engines

Most commercial search engines provide a mechanism to determine the number of backlinks they have recorded to a particular web page. For example, Google can be searched using link:wikipedia.org to find the number of pages on the Web pointing to http://wikipedia.org/. Google only shows a small fraction of the number of links pointing to a site. It credits many more backlinks than it shows for each website.

Technical

When HTML (Hyper Text Markup Language) was designed, there was no explicit mechanism in the design to keep track of backlinks in software, as this carried additional logistical and network overhead.

Some website software internally keeps track of backlinks. Examples of this include most wiki and CMS software.

Other mechanisms have been developed to track backlinks between disparate webpages controlled by organizations that aren't associated with each other. The most notable example of this is TrackBacks between blogs.

See also

• Link farms
• Methods of website linking
• PageRank
• Search Engine Optimization
• Linkback

References

• Lennart Björneborn and Peter Ingwersen (2004). "Toward a Basic Framework for Webometrics". Journal of the American Society for Information Science and Technology 55 (14): 1216–1227. doi:10.1002/asi.20077. http://www3.interscience.wiley.com/cgi-bin/abstract/109594194/ABSTRACT.