nofollowwas designed by Google’s head of webspam team Matt Cutts and Jason Shellen from Blogger.com in 2005.
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, 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.
nofollowattribute 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 a search engine spider should or should not do with the content of the crawled page.
rel="nofollow"attribute would not influence the link target's PageRank. In addition, the Yahoo and Windows Live search engines also respect this tag.
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 tell a search engine: "Do not follow any of the hyperlinks in the body of this document.".
|rel="nofollow" Action||Yahoo!||MSN Search||Ask.com|
|Follows the link||Yes||Yes||Not proven||Yes|
|Indexes the "linked to" page||No||Yes||No||Yes|
|Shows the existence of the link||Only for a previously indexed page||Yes||No||Yes|
|In SERPs for anchor text||Only for a previously indexed page||Yes||No||Yes|
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). However, there are several free plugins available that automatically remove the
nofollow attribute value.
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.
Following increasing spam problems and a within-Foundation order from Jimmy Wales,
rel="nofollow" was added to article-space links in January 2007. 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.
A number of social bookmarking and photo sharing websites also use the
rel="nofollow" tag for their outgoing links, including: Digg.com, Furl, Propeller.com (formerly Netscape.com), Yahoo! My Web 2.0, YouTube, and Technorati Favs.
nofollowattribute to prevent comment spam is in doubt and raises other issues instead, search engines have moved ahead and attempted to repurpose the attribute for something different. Google began suggesting the use of
nofollowalso as a machine-readable disclosure for paid links, so that these links do not get credit in search engines results.
The growth of the link buying economy, where companies' entire business models are based on paid links that affect search engine rankings, 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. This triggered a very strong response from web masters.
nofollowattribute to control the flow of PageRank within a website. This is an entirely different use than it was intended originally.
Nofollowwas designed to control the flow of PageRank from one website to another. However, some SEOs have suggested that a
nofollowused for an internal link should work just like
nofollowused for external links.
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.
The practice is controversial and has been challenged by some SEO professionals, including Shari Thurow and Adam Audette . 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 (see Matt's clarifying comment, rebutting the attributed statement ) 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 has publicly advised Webmasters NOT to use
nofollow on internal links.
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.
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.
rel="nofollow", arguing, for example, that
rel="nofollow"in order to reduce the effect of heavy inter-blog linking on page ranking.