I recently read a post by Lina Robertson on linking from comments, and I wanted to divulge into the topic a little more. I have been researching this topic quite a bit lately, and I think I can add to her conversation.

What is a NoFollow Link?

A nofollow links main purpose is to tell Google not to follow a link.  That means Google does not pass PageRank,  or the anchor text for those links. Which means, Google does not count nofollow links, does not follow them, and no-following a link let's you tell Google that you don't trust a certain site. 

Examples:

NoFollow link: <a href="www.activerain.com" rel="nofollow">ActiveRain</a>

DoFollow link: <a href="www.activerain.com"> ActiveRain</a>

The difference is pretty obvious, and it's really easy to add the nofollow attribute to any link you want.

Google's Suggestions For NoFollow Links

Untrusted Content - It's good practice to put the no-follow attribute on links you don't trust. ActiveRain adds the no-follow attribute to your comments section, because you never know who is going to comment on your blog, you can't really trust people you don't know, and that makes comments a good place to use no-follow.

Paid Links - It is widely known that Google frowns upon paid links, such as when a webmaster pays another webmaster for a link to increase their PageRank, this is Black Hat SEO, and could get you banned form search engines. However, links that are purchased for advertising should are ok, but you should add the no-follow attribute so Google doesn't think you are buying links for PageRank.

Read: Google's Webmaster Page On NoFollow Links

How do you tell if a link is nofollow?

There are two ways to tell if a link is nofollow that I know of.

#1. If you don't use Firefox you will need to look at the code of a webpage. This is the hard way, and I wouldn't recommend it, but I will still show you how.

Fiirst you need to go to your toolbar on your browser, click "view," scroll down to "page source" or "Source" and look at the coding on the page.

Then you can search for the links anchor text by hitting "Ctrl F" on your keyboard, and search for nofollow or the anchor text of the link.

If that seems diffucult for you, your right, it is. There is an easier way, and here's how:

#2. First, you have to use Firefox, if you don't use Firefox, you can download it here: Download Firefox

Now that you have firefox, you need to get a plug in that will highlight nofollow links, you can download it here: SearchStatus Downlaod

Now that you have downloaded your plug in, you should see something like this on your browser toolbar. (Sometimes it shows up at the bottom of your browser, or the top.)

Now just right click the little @ button next to the left arrow, and you should get a drop down menu, click the "Highlight NoFollow Links" and voila! All nofollow links are then highlighted on your web pages. 

And this is what a nofollow link looks like:

What's the big deal of all this?

The main benefit of knowing whether links are nofollow or not is for SEO purposes.  If you know anything about SEO, you know that links are the #1 determining factor for search engine rankings. But it does no good to go after links for your search engine rankings, for Google anyways, if they are nofollow.  Nofollow links are still good links to drive traffic to your websites, like if people click on them to go to your site, but from a Google stand point, they aren't going to pass any weight for your search engine rankings.

MUST KNOW!

NoFollow is for Google only, Yahoo! and Bing do not use nofollow linking techniques. This is important to know because even though a link is nofollow, it still may be a good link in Yahoo! or Bing, and I would recommend that you don't only  go after nofollow links for your SEO strategy.

Here's Why NoFollow Links Are Good

If Google notices that you only have dofollow links pointing to your website, it's going to throw up read flags. Google knows that having nofollow and dofollow links is natural, and if all of your links are dofollow, that doesn't look natural to Google. If you don't look natural, your site could get penalized.

Yahoo and Bing do not care about a nofollow link or a dofollow link, they count all links. Because they count all links, the more high quality links you have, even if they are nofollow, the higher you are going to rank in those search engines.

If you have any questions, let me know and I will try to answer them to the best of my ability. It would also be nice to hear some of the experts around Active Rain on their input of the nofollow link.