I’ve been working on SEO (search engine optimization) code this weekend, mostly for my Word Tips site and also with a client.
I do some freelance WordPress work here in China where corporate blogging is now taking off.
During lunch we got talking about different SEO tricks, amongst which was the ‘no-follow’ attribute.
This was new to my colleagues, so I gathered some material from Wikipedia and sent it to them. FWIW here’s how it works.
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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 spam-indexing from occurring.
Concept and specification
The concept for the specification of the attribute value
nofollow was designed by Matt Cutts (Google) 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
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.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.
Google Take Action
In 2005 Google announced that hyperlinks with rel="nofollow"
attribute would not influence the link target’s PageRank. In
addition, the Yahoo and Windows Live search engines also respect
this attribute.
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
does tell a search engine: “Do not follow any of the
hyperlinks in the body of this document.”.
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.
- 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. - Yahoo “follows it”, but excludes it from their ranking calculation.
- MSN 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 ignores the attribute altogether.
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.
Websites that don’t use the rel="nofollow" tag include Digg, Furl, and My Web 2.0.
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.
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.
Control internal PageRank flow
Search engine optimization professionals started using the nofollow attribute to control the flow of PageRank within a website. 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.
If you have any thoughts on this, please let me know.
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