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Introduction nofollow

nofollow is an HTML attribute value (no_follow) 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.
(more on Wikipedia)

Google introduced the no_follow attribute in 2005 to prevent comment spam and trackback spam: Official Google Blog: Preventing comment spam

Two kinds of no_follow

The robots exclusion standard, also known as the Robots Exclusion Protocol or robots.txt protocol is a convention to prevent cooperating web spiders and other web robots from accessing all or part of a website which is, otherwise, publicly viewable.

For example:
"Do not follow any of the hyperlinks in the body of this document." (Wikipedia)

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."

Research questions (C. Tatum):

  • How prevalent is the nofollow tag?
  • What percent of a given network is excluded from a internet search due to nofollow?
  • Assuming that nofollow segregates content, is there a way to search the internet as a whole?
  • What are the social/political implications of this sort of segregation?
  • What do we loose by dividing our primary access to the web into two primary entry frames, blogs and not-blogs?

Prevalence of the no_follow tag

Blog software

  • WordPress: default (do_follow plugin)
  • Blogger:
  • Typepad: "For TypePad subscribers, implementation will be automatic. Links from commenters will be flagged automatically in the next update, which will be deployed within the next 24 hours." (Six Apart - Support for Nofollow)
  • Movable Type: "For Movable Type users, we’re shipping a plugin today to enable support on Movable Type-powered sites. The Movable Type website has full details, including a download link." (Six Apart - Support for Nofollow)
  • LiveJournal: "LiveJournal also plans to implement the specification for comments from other members who are not friends." (Six Apart - Support for Nofollow)


Google vs. Google blog search vs. Technorati

How does Google segregate the static web and blogs? Does No_Follow play a role?

See here for speculation on how their blog search works.

From About Google Blog Search:

  • Which blogs are included in Blog Search? The goal of Blog Search is to include every blog that publishes a site feed (either RSS or Atom). It is not restricted to Blogger blogs, or blogs from any other service.

  • How do I get my blog listed? If your blog publishes a site feed in any format and automatically pings an updating service (such as Google Blog Search Pinging Service), we should be able to find and list it. Also, we will soon be providing a form that you can use to manually add your blog to our index, in case we haven't picked it up automatically. Stay tuned for more information on this.

More reading material

Search Engine Support (2005, todo: check current status)

rel="nofollow" Action   Google   Yahoo   MSN Search
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

-- Main.annehelmond - 25 Jul 2007

-- Main.cliffordtatum - 25 Jul 2007

  • Google Blog Search MOM inlink results TAG CLOUD:

  • Google Search MOM inlink results Tag Cloud:

  • Technorati Search MOM inlink results Tag Cloud:

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Topic revision: r2 - 31 Aug 2007, ErikBorra
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