nofollow is a non-standard HTML attribute value used to instruct search engines that a hyperlink should not influence the link target's ranking in the search engine's index. It is intended to reduce the effectiveness of certain types of spamdexing, thereby improving the quality of search engine results and preventing spamdexing from occurring in the first place. HTML, short for Hypertext Markup Language, is the predominant markup language for web pages. ... Spamdexing or search engine spamming is the practice of deliberately creating web pages which will be indexed by search engines in order to increase the chance of a website or page being placed close to the beginning of search engine results, or to influence the category to which the page...

Concept and specification

The concept for the specification of the attribute value nofollow was designed by Google’s head of webspam team Matt Cutts and Jason Shellen from Blogger.com in 2005.^[1] Matt Cutts (left, with Chris Hooley) Matt Cutts works for the quality group in Google, specializing in search engine optimization issues. ...

The specification for nofollow is (C) 2005-2007 by the authors and subject to a royalty free patent policy, e.g. per the W3C Patent Policy 20040205,^[2] and IETF RFC3667^[3] & RFC3668.^[4] The authors intend to submit this specification to a standards body with a liberal copyright/licensing policy such as the GMPG, IETF, and/or W3C.^[1] The Internet Engineering Task Force (IETF) is charged with developing and promoting Internet standards. ... The World Wide Web Consortium (W3C) is a consortium that produces standards—recommendations, as they call them—for the World Wide Web. ...

What nofollow is not for

The nofollow attribute value is not meant for blocking access to content or preventing content to be indexed by search engines. The proper methods for blocking search engine spiders to access content on a website or for preventing them to include the content of a page in their index are the Robots Exclusion Standard (robots.txt) for blocking access and on page Meta Elements that are designed to specify on an individual page level, what search engine spider should or should not do with the content of the crawled page. The robots exclusion standard or robots. ... Meta elements are HTML or XHTML elements used to provide structured metadata about a web page. ...

Introduction and support

Google announced in early 2005 that hyperlinks with rel="nofollow" attribute^[5] would not influence the link target's PageRank. In addition, the Yahoo and MSN search engines also respect this tag.^[6] This article is about the corporation. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... How PageRank Works PageRank is a link analysis algorithm 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. ...

How the attribute is being interpreted differs between the search engines. While some take it literally and do not follow the link to the page being linked to, others still "follow" the link to find new web pages for indexing. In the latter case rel="nofollow" actually tells a search engine "Don't score this link" rather than "Don't follow this link." This differs from the meaning of nofollow as used within a robots meta tag, which does tells a search engine: "Do not follow any of the hyperlinks in the body of this document.". The robots exclusion standard or robots. ...

Interpretation by the individual search engines

While all engines that support the attribute exclude links that use the attribute from their ranking calculation, the details about the exact interpretation of the attribute vary from search engine to search engine.^[7][8]

• Google takes "nofollow" literally and does not "follow" the link at all. That is supposedly their official statement, but experiments conducted by SEOs show conflicting results. They show instead that Google does follow the link, but does not index the linked-to page, unless it was in Google's index already for other reasons (such as other, non-nofollow links that point to the page).^[8] Links with NOFOLLOW are included in the back-links reporting data at Google's Webmaster Central.^[9]
• Yahoo! "follows it", but excludes it from their ranking calculation.
• MSN Search respects "nofollow" as regards not counting the link in their ranking, but it is not proven whether or not MSN follows the link.
• Ask.com does not use the attribute for anything.

This article is about the corporation. ... A typical search results page Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via natural (organic or algorithmic) search results. ... “Yahoo” redirects here. ... MSN Searchs homepage viewed in Microsoft Internet Explorer 6. ... Ask. ...

Usage by weblog software

Most weblog software marks reader-submitted links this way by default (with no option to disable it without code modification). A more sophisticated server software could spare the nofollow for links submitted by trusted users like those registered for a long time, on a whitelist, or with a high karma. Some server software adds rel="nofollow" to pages that have been recently edited but omits it from stable pages, under the theory that stable pages will have had offending links removed by human editors. In psychology and sociology, a trust metric is a measure of how a member of a group is trusted by the other members. ... Look up whitelist in Wiktionary, the free dictionary. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ...

The widely used blogging platform Wordpress version 1.5 and above automatically assigns the nofollow attribute to all user-submitted links (comment data, commenter URI, etc).^[10] This article is about the self-hosted blog software. ...

Usage on other websites

MediaWiki software, which powers Wikipedia, was equipped with nofollow support soon after initial announcement in 2005. The option was enabled on most international Wikipedias. One of the prominent exceptions was the English language one. Initially, after a discussion, it was decided not to use rel="nofollow" in articles and to use a URL blacklist instead. In this way, English Wikipedia contributed to the scores of the pages it linked to, and expected editors to link to relevant pages. For the organization that manages Wikipedia and its sister projects, see Wikimedia Foundation. ... Wikipedia (IPA: , or ( ) is a multilingual, web-based, free content encyclopedia project, operated by the Wikimedia Foundation, a non-profit organization. ...

In May 2006, a patch to MediaWiki software allowed to enable nofollow selectively in namespaces. This functionality was used on pages that are not considered to be part of the actual encyclopedia, such as discussion pages and resources for editors.^[11] Following increasing spam problems and a within-Foundation order from Jimmy Wales, rel="nofollow" was added to article-space links in January 2007;^[12].^[13] However, the various interwiki templates and shortcuts that link to other Wikimedia Foundation projects and many external wikis such as Wikia are not affected by this policy. In general, a namespace is an abstract container, which is or could be filled by names, or technical terms, or words, and these represent (stand for) real-world things. ... Jimmy Donal Jimbo Wales, (born August 7, 1966)[2] is an American Internet entrepreneur best known for his role in founding Wikipedia, as well as other wiki-related projects, including the charitable organization Wikimedia Foundation, and the for-profit company Wikia, Inc. ... For the wiki software used and developed by the Wikimedia Foundation, see MediaWiki. ... Wikia (no official pronunciation[2]; originally Wikicities) is a selective wiki hosting service (or wiki farm) operated by Wikia, Inc. ...

Other websites like Slashdot, with high user participation, use improvised nofollow implementations like adding rel="nofollow" only for potentially misbehaving users. Potential spammers posing as users can be determined through various heuristics like age of registered account and other factors. Slashdot also uses the poster's karma as a determinant in attaching a nofollow tag to user submitted links. Slashdot, often abbreviated as /.[1], is a science, science fiction, and technology-related news website owned by SourceForge, Inc. ...

Repurpose for paid links

While the effectiveness of the nofollow attribute to prevent comment spam is in doubt and raises other issues instead,^[14] search engines have moved ahead and attempted to repurpose the attribute for something different. Google began suggesting the use of nofollow also as a machine-readable disclosure for paid links, so that these links do not get credit in search engines results.^[15]

The growth of the link buying economy, where company's entire business model is based on paid links that affect search engine rankings,^[16] caused the debate about the use of nofollow in combination with paid links to move into the center of attention of the search engines, who started to take active steps against link buyers and sellers.^[17] This triggered a very strong response by the web master community in return and also raised new questions that need to be answered.^[18]

Criticism

Some weblog authors object to the use of rel="nofollow", arguing, for example,^[19][20] that

• Link spammers will continue to spam everyone to reach the sites that do not use rel="nofollow"
• Link spammers will continue to place links for clicking (by surfers), even if those links are ignored by search engines.
• Google is advocating the use of rel="nofollow" in order to reduce the effect of heavy inter-blog linking on page ranking.

See also

• Spam in blogs and nofollow
• Google PageRank
• Search engine optimization
• Search engine spiders, also called web crawlers

Blocking and excluding content from search engines

• Robots Exclusion Standard (robots.txt)
• Meta Elements

Spam in blogs (also called simply blog spam or comment spam) is a form of spamdexing. ... Spam in blogs (also called simply blog spam or comment spam) is a form of spamdexing. ... How PageRank Works PageRank is a link analysis algorithm 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. ... A typical search results page Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via natural (organic or algorithmic) search results. ... A web crawler (also known as a Web spider or Web robot) is a program or automated script which browses the World Wide Web in a methodical, automated manner. ... The robots exclusion standard or robots. ... Meta elements are HTML or XHTML elements used to provide structured metadata about a web page. ...

References