nofollow

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nofollow is an HTML attribute value used to instruct some 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 search engine spam, thereby improving the quality of search engine results and preventing spamdexing from occurring.

Contents

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]

The nofollow HTML attribute was originally designed to stop comment spam on blogs. Blog readers and bloggers were well aware of the immense problem. Just like any other type of spam affects its community, comment spam affected the entire blogging community, so in early 2005 Google’s Matt Cutts and Blogger’s Jason Shellen designed the attribute to address the problem and the nofollow attribute was born.[2]

The specification for nofollow is copyrighted 2005-2007 by the authors and subject to a royalty free patent policy, e.g. per the W3C Patent Policy 20040205,[3] and IETF RFC 3667 & RFC 3668. 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]

Example

<a href="http://www.example.com/" rel="nofollow">discount drugs</a>

What nofollow is not for

The nofollow attribute value is not meant for blocking access to content, or for 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 a search engine spider should or should not do with the content of the crawled page.

Introduction and support

Google announced in early 2005 that hyperlinks with rel="nofollow" attribute[4] would not influence the link target's PageRank. In addition, the Yahoo and Bing search engines also respect this attribute.[5][6]

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[citation needed], 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 tell a search engine: "Do not follow any of the hyperlinks in the body of this document.".

On June 15 2009, Matt Cutts, a well known software engineer of Google, announced that Google Bot will no longer treat nofollowed links in the same way, in order to prevent SEOs from using nofollow for PageRank Sculpting. As a result of this change the usage of nofollow leads to evaporation of pagerank. In order to avoid the above, SEOs developed alternative techniques that replace nofollowed tags with obfuscated Javascript and thus permit PageRank Sculpting. Additionally several solutions have been suggested that include the usage of iframes, flash and javascript.

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 states that their engine takes "nofollow" literally and does not "follow" the link at all. However, experiments conducted by SEOs show conflicting results. These studies reveal 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][9]
  • Yahoo! "follows it", but excludes it from their ranking calculation.
  • Bing respects "nofollow" as regards not counting the link in their ranking, but it is not proven whether or not Bing follows the link.
  • Ask.com ignores the attribute altogether.[citation needed]
rel="nofollow" Action Google Yahoo! Bing Ask.com
Uses the link for ranking No No No Yes
Follows the link Yes Yes Yes Yes
Indexes the "linked to" page No Yes No Yes
Shows the existence of the link Only for a previously indexed page Yes Yes Yes
In results pages for anchor text Only for a previously indexed page Yes Only for a previously indexed page Yes

Use by weblog software

Most weblog software marks reader-submitted links this way by default (with no option to disable it, except for modification of the software's code). 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 an acceptable karma level. 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.

The widely used blogging platform WordPress versions 1.5 and above automatically assign the nofollow attribute to all user-submitted links (comment data, commenter URI, etc).[10] However, there are several free plugins available that automatically remove the nofollow attribute value.[11]

Use 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 Wikipedias. One of the prominent exceptions was the English Wikipedia. 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.

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.[12] Following increasing spam problems and a within-Foundation order from Jimmy Wales, rel="nofollow" was added to article-space links in January 2007.[13][14] 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.

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.

Social bookmarking and photo sharing websites that use the rel="nofollow" tag for their outgoing links include YouTube and Digg.com[15] (for most links); websites that don't use the rel="nofollow" tag include Propeller.com (formerly Netscape.com), Yahoo! My Web 2.0, and Technorati Favs.[16]

Repurpose

Paid links

Search engines have attempted to repurpose the nofollow 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.[17]

The growth of the link buying economy, where companies' entire business models are based on paid links that affect search engine rankings,[18] 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.[19] This triggered a very strong response from web masters.[20]

Control internal PageRank flow

Search engine optimization professionals started using the nofollow attribute to control the flow of PageRank within a website, but google since corrected this error, and any link with nofollow attribute decreases the PR that the page can pass on[21]. This practice is known as PageRank sculpting. This is an entirely different use than it was intended originally. nofollow was designed to control the flow of PageRank from one website to another. However, some SEOs have suggested that a nofollow used for an internal link should work just like nofollow used for external links.

Several SEOs have suggested that pages such as "About Us", "Terms of Service", "Contact Us", and "Privacy Policy" pages are not important enough to earn PageRank, and so should have nofollow on internal links pointing to them. Google employee Matt Cutts has provided indirect responses on the subject, but has never publicly endorsed this point of view.[22]

The practice is controversial and has been challenged by some SEO professionals, including Shari Thurow[23] and Adam Audette.[24] Site search proponents have pointed out that visitors do search for these types of pages, so using nofollow on internal links pointing to them may make it difficult or impossible for visitors to find these pages in site searches powered by major search engines.

Although proponents of use of nofollow on internal links have cited an inappropriate attribution to Matt Cutts[25] (see Matt's clarifying comment, rebutting the attributed statement)[26] as support for using the technique, Cutts himself never actually endorsed the idea. Several Google employees (including Matt Cutts) have urged Webmasters not to focus on manipulating internal PageRank. Google employee Adam Lasnik[27] has advised webmasters that there are better ways (e.g. click hierarchy) than nofollow to "sculpt a bit of PageRank", but that it is available and "we're not going to frown upon it".

No reliable data has been published on the effectiveness or potential harm that use of nofollow on internal links may provide. Unsubstantiated claims have been challenged throughout the debate and some early proponents of the idea have subsequently cautioned people not to view the use of nofollow on internal links as a silver bullet or quick-success solution.[citation needed]

More general consensus seems to favor the use of nofollow on internal links pointing to user-controlled pages which may be subjected to spam link practices, including user profile pages, user comments, forum signatures and posts, calendar entries, etc.[citation needed]

YouTube, a Google company, uses nofollow on a number of internal 'help' and 'share' links.[citation needed]

See also

Blocking and excluding content from search engines

References

  1. 1.0 1.1 rel="nofollow" Specification, Microformats.org, retrieved June 17, 2007
  2. "The nofollow Attribute and SEO". Published-Articles.com. May 22, 2009. http://www.published-articles.com/Art/18844/136/The-nofollow-Attribute-and-SEO.html. Retrieved September 8, 2009. 
  3. W3C Patent Policy 20040205,W3.ORG
  4. W3C (December 24, 1999), HTML 4.01 Specification, W3C.org, retrieved May 29, 2007
  5. Google (January 18, 2006), Preventing comment spam, Official Google Blog, retrieved on May 29, 2007
  6. Microsoft (June 3, 2008), [1], "Bing Community", retrieved on June 11, 2009
  7. Loren Baker (April 29, 2007),How Google, Yahoo & Ask.com Treat the No Follow Link Attribute, Search Engine Journal, retrieved May 29, 2007
  8. 8.0 8.1 Michael Duz (December 2, 2006),rel=”nofollow” Google, Yahoo and MSN, SEO Blog, retrieved May 29, 2007
  9. Rel Nofollow Test from August 2007
  10. Codex Documentation, Nofollow, Wordpress.org Documentation, retrieved May 29, 2007
  11. WordPress Plugins, Plugins tagged as Nofollow, WordPress Extensions, retrieved March 10, 2008
  12. Wikipedia (May 29, 2006), Wikipedia Signpost/2006-05-29/Technology report, Wikipedia.org, retrieved May 29, 2007
  13. Brion Vibber (January 20, 2007), Nofollow back on URL links on en.wikipedia.org articles for now, Wikimedia List WikiEN-l, retrieved May 29, 2007
  14. Wikipedia:Wikipedia Signpost/2007-01-22/Nofollow
  15. John Quinn (September 2, 2009), Recent Changes to NOFOLLOW on External Links, Digg the Blog, retrieved on September 3, 2009
  16. Loren Baker (November 15, 2007), Social Bookmarking Sites Which Don’t Use NoFollow Bookmarks and Search Engines, Search Engine Journal, retrieved on December 16, 2007
  17. Matt Cutts (September 1, 2005), Text links and PageRank, Matt Cutts Blog, retrieved June 17, 2007
  18. Philipp Lenssen (April 19, 2007), The Paid Links Economy,Google Blogoscoped, retrieved June 17, 2007
  19. Matt Cutts (April 14, 2007 ), How to report paid links, Matt Cutts Blog, retrieved June 17, 2007
  20. Carsten Cumbrowski (May 14th, 2007), Matt Cutts on Paid Links Discussion - Q&A, SearchEngineJournal.com, retrieved June 17, 2007
  21. http://www.mattcutts.com/blog/pagerank-sculpting/
  22. October 8, 2007, Eric Enge Interviews Google's Matt Cutts, Stone Temple Consulting, retrieved on January 20, 2008.
  23. March 6, 2008, You'd be wise to "nofollow" this dubious advice, Search Engine Land.
  24. June 3, 2008 8 Arguments Against Sculpting PageRank With Nofollow, Audette Media.
  25. August 29, 2007 Matt Cutts on Nofollow, Links-Per-Page and the Value of Directories, SEomoz.
  26. August 29, 2007 [2], SEOmoz comment by Matt Cutts.
  27. February 20, 2008 Interview with Adam Lasnik of Google


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