Nofollow Links Affect Google Search Engine Ranking

Résultat de recherche d'images pour "seo"Though the myth that nofollow links are not being indexed by search engines is still being perpetuated amongst webmasters and SEO gurus alike, the truth is that nofollow links actually are being indexed and are affecting search engine ranking. In late 2008, Google began to index links that contained the rel=nofollow attribute.

What is PageRank and How is it Calculated?

Web designers can think of Google PageRank as a reputation system, commonly used in many forums to indicate how many useful posts a user has made. It’s a value that the Google search engine uses to calculate the importance of any given web page found in its index. Though Google has not disclosed the exact calculations used to assign PageRank, they have given web masters enough information that a simple model can be used to describe PageRank calculation.

For this simplified example, Page A, B and C each have assigned 30 points of reputation. If Page A links to Page B and Page C, the 30 points of reputation from Page A are evenly divided amongst Page B and Page C and added to their respective reputations. Page B and Page C each total 45 points of reputation with the links from Page A.

To prevent infinite loops from occurring in this system, Google PageRank has a built in decay of approximately 10 to 15% that is calculated before PageRank is distributed. Factoring this decay into the example above, Page A is actually passing 13.5 points of reputation to Page B and Page C.

But with the introduction of the nofollow link in 2005, webmasters were able to control their votes for reputation. If Page A linked to Page B with a dofollow link, but linked to Page C with a nofollow link, then all 27 points of reputation would flow to Page B and Page C would receive no points of reputation.

How Nofollow Links Were Being Used and Abused

The nofollow link was originally meant to give web designers a tool to combat the spammers that plagued blogs and forums of more legitimate web sites. This gave Page A the ability to tell search engines that it did not wish to vote for Page C’s reputation.

However, an unintended side effect of the nofollow attribute allowed web designers to use the nofollow link to control the flow of PageRank within their own websites. If a web designer wanted only certain pages to rank highly in search engines, he would funnel all PageRank from the web site into the desired pages by using nofollow links for all other links on his site. This prevented Google from indexing a lot of high quality content that users might be searching for.

According to a blog posted on June 15, 2009 by Google guru, Matt Cutts, in an effort to better serve its customers Google began indexing links that contained the rel=nofollow attribute in late 2008. No formal announcement was made of this change; Google assumed that webmasters would notice the changes and modify their sites accordingly.

What Does This Really Mean for SEO?

This change affected the calculations Google uses to determine PageRank. Now, when Page A gives Page B a dofollow link and gives Page C a nofollow link, Google calculates the PageRank distribution as if both pages B and C were receiving PageRank. Page B receives 13.5 points of PageRank, but the remaining points that would have gone to Page C are simply lost.

This could possibly be bad news for web designers that had previously used PageRank sculpting to control the flow of PageRank within their web sites, as it unnecessarily reduces the total amount of PageRank that can flow within the site.

That is the “official” word from Google. However, there is a hotly contested debate surrounding this issue amongst those in the SEO community. Some webmasters believe that nofollow links have little value for SEO other than the traffic they might directly bring to a website, while others believe that the relevance in terms of content and context of a nofollow link can make the linked page perform better for targeted keywords.

And It is a well documented fact that Google is recording nofollow links as backlinks for websites. Webmasters need only consult their backlinks from Google’s Webmaster Tools to verify this, and there are numerous threads about this phenomenon in webmaster forums. They can also buy links from other webmasters.

The best advice for a webmaster seeking better ranking for highly competitive keywords is to investigate what the top ranking competitors have done to achieve their ranking.