There are two types of nofollow attributes that I am going to cover in this post. The first is the nofollow link attribute and the second is the nofollow HTML attribute. To understand a little more about the two, take a look at this YouTube video by Matt Cutts at Google who explains how NoFollows effect your site.
The NoFollow HTML attribute
Originally this was created by Matt Cutts and Jason Shellen from Google and Blogger to prevent people from spaming the comments of blogs so that spammers could not pick up pageRank, Link Juice or Anchor Text Value from a link posted in someones comments.
<meta name="robots" content="nofollow" />
The above attribute tells some search engines like Google and Bing to not crawl any of the outgoing links on the page.
The NoFollow Link Attribute
Later on Matt and his team came up with the rel=”nofollow” link attribute that allowed you to target which links in your site you wanted to transfer pageRank and link juice.
<a href="outgoinglinksite.php" rel="nofollow">This link will not be followed</a>
This seemed to work well as owners of blogs and websites could asign which outgoing links on their site they wanted to give value.
How search engines treat NoFollows
As shown above, Google & Bing do actually follow a link with a nofollow attribute but does not give the link any link value or link juice. The followed page is also not indexed by Google or Bing.
Other search engines like ASK and Yahoo completely ignore the nofollow tag and will follow and index the page or linked pages.
WordPress Plugins that manage nofollow links
Platinum SEO Plugin can handle all your nofollow needs, this plugin can turn off the auto-nofollow that WP sites have by default. Using this plugin you can remove all nofollows for your internal pages.
WordPress SEO by Yoast: This is probably the smartest and most comprehensive SEO plugin and allows you to add nofollows at a page level as well as a category level.
Firefox Plugin to detect nofollow links
Search Status: This firefox plugin has a neat highlight feature to detect nofollow links so you can see if the sites linking to you are sharing the love.
My opinion on NoFollow
Do not go and nofollow all your outgoing links (and do not nofollow internal links), give credit where credit is deserved. I actually think that putting nofollows all over your site may hurt your listing in Google. I believe that just the fact that you are adding nofollows to your site means that you are doing this for one reason… to keep the link love for yourself and your SEO company has told you to do this. Well let me throw a spanner in the works… if SEO companies are all doing this then Google is sure to catch onto to this and as always I am sure Google has compensated for this. In other words I would not be surprised that if nofollows exist on your site Google may profile your page as “SEO’d” and in the end give less value to your page. I recommend that you do not use nofollow links at all on your internal pages and keep your nofollows as natural as possible and don’t go overboard with your page sculpting for external nofollow links.