This is a question I get all the time. In short, the nofollow attribute in HTML is a way for you to tag a link to suggest to the search engines that they ignore this link’s existence. When I say ‘ignore the link’, I mean that Google won’t use the link for any of the 3 ways that Google uses links. That means they won’t visit the link to find new content, they won’t give link popularity through it, and they won’t take the anchor text as a clue for what keyword the content should rank for.
How do you Implement a Nofollow?
If your normal HTML link looks like this:
<a href=”http://www.site.com>Clickable Anchor Text</a>
When you nofollow a link, it will look like this:
<a rel=”nofollow” href=http://www.site.com>Clickable Anchor Text</a>
That’s it! Just slip the rel=”nofollow” code into any link, and you’re done. You can place it before or after the href attribute – the order doesn’t matter.
Why would anyone put a nofollow on a link?
The original reason that Google adopted nofollow tags was to combat spam.
The nofollow attribute is extremely helpful for sites like Twitter and Facebook to combat spam (if you could get SEO credit for linking to yourself from a twitter or FB account, wouldn’t you create hundreds of spam accounts just to link to yourself?), so instead they automatically nofollow every link, keeping would-be spammers at bay. This also keeps the Fail Whale at bay because the extra resources required to sustain large amounts of spam would be sizable. Just ask Digg.
Another reason you would nofollow a link would be to abide by Google’s advertiser guidelines.
Google recommends that whenever a link it sponsored, that it be tagged with the nofollow code. This helps stay within Google’s guidelines because they don’t ever want a site to be able to pay for rankings. If we were being paid to put a PageRank-passing link on our site, we are going against the Goog’s terms of service. By simply adding a nofollow to advertisements, it ensures that money can’t buy rankings.
There are many other cases where you might consider adding a nofollow link. Consider nofollowing links that direct users to a resource undeserving of credit. For instance, if you create a PDF document, and you want people to view your work, they must have Adobe Reader installed to view the file, so you would likely link to Adobe Reader so your readers can download it in order to see your work. I personally don’t think Adobe is deserving of receiving link popularity from my site when the PDF was my own creation.
When Shouldn’t You Employ a Nofollow?
There are several situations where nofollows have been used where they shouldn’t be. For instance, if your competitor embarrassed himself, and you might want to link to them to point it out. Then you obviously thought to yourself that he is unworthy of a link from your site because the search engines would see that as a valuable link for your competitor. Your next thought was to nofollow the link to make sure it doesn’t pass popularity, right?
Fight the temptation!
Google publicly began making its own judgments about whether or not a link was deserving of a nofollow back in July ’09. This means that Google is going to look at the link and decide whether or not it should be nofollowed. What does Google take into account when determining the validity of your nofollow? I don’t know, but I do know you can’t afford to be giving your competitor a solid link.
You may also be tempted to nofollow your internal links in order to preserve PageRank for your most important pages (also called PageRank sculpting). Again, fight the temptation!
The original reason that Google started exercising its own judgment on nofollows was actually to stop PR sculpting. When you can up your web rankings simply by jettisoning parts of your site with nofollows, and not having to create fresh or interesting content, it’s likely not a lasting strategy. That means it’s not going to work, and you should forget about it.