The rel=”nofollow” attribute is something that has come about in the last 5 or 6 years, and was recognised by Google in 2005. It is a way to indicated that the link you are using may not be trustworthy. From the beginning, search engines look at links as a way of providing authority, or recommendations. Nofollow links allow you to link to a page, whilst also say “I don’t trust this site”. Matt Cutts recommends you use the nofollow tag wherever there are links created that you do not have direct control over. This includes wikis, search pages, profile pages on forums etc.
How Does Google Handle Nofollow links?
In general, they say they don’t follow them. This means that Google does not transfer PageRank or anchor text across these links. However, this goes directly against the webmaster guidelines, which says that you should not manipulate PageRank in any way. So it is expected that Google places some value on Nofollow links. Most other search engines adopt a similar strategy, although the value of nofollow links seems to fluctuate from one season to the next. On June 15, 2009, Matt Cutts, stated that GoogleBot will no longer treat nofollowed links in the same way, in order to prevent webmasters from using nofollow for PageRank Sculpting.
What about rel=”nofollow me”?
If you host user profiles and allow users to link to other profiles on the web, Google encourages you to mark those links with the rel=”me” microformat so that they can be made available through the Social Graph API. For example:
<a href="http://blog.example.com" rel="me">My blog</a>
However, because these links are user-generated and may sometimes point to untrusted pages, we recommend that these links be marked with nofollow. For example:
<a href="http://blog.example.com" rel="me nofollow">My blog</a>
With rel=”me nofollow”, Google will continue to treat the rel=”nofollow” as expected for search purposes, such as not transferring PageRank. However, for the Social Graph API, we will count the rel=”me” link even when included with a nofollow.
