From Wikipedia, the free encyclopedia

nofollow is an 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. Google announced in early 2005 that hyperlinks with rel="nofollow" attribute^[1] would not influence the link target's PageRank. In addition, the Yahoo and MSN search engines also respect this tag.^[2]

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" has come to be regarded as a microformat.

Contents 1 Usage by weblog software 2 Criticism 3 See also 4 References

Using rel="nofollow" is a much easier solution that makes using improvised techniques irrelevant. Most weblog software now 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.

Some weblog authors object to the use of rel="nofollow", arguing, for example,^[3] 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

In particular, on the English Wikipedia, after a discussion, it was decided not to use rel="nofollow" in articles and to use a URL blacklist instead. In this way, Wikipedia contributes to the scores of the pages it links to, and expects editors to link to relevant pages. However, Wikipedia does use rel="nofollow" on pages that are not considered to be part of the actual encyclopedia, such as discussion pages, and Wikipedia projects in languages other than English also use it in articles.^[4] Following increasing spam problems and a within-Foundation order from Jimmy Wales, rel="nofollow" was added to article-space links again in January 2007;^[5] however, the various interwiki templates and shortcuts that promote other Wikimedia Foundation projects, the for-profit entity of Wikia and its wikis, and other domains, appear to be unaffected by this rel="nofollow" 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.

• Spam in blogs