You don’t have to be very deep into SEO before running into the nofollow discussion. Back in ancient days (2005) Google announced that they would not pass any credit when they ranked websites in their search results that used that attribute . Other search engines agreed to use to honor the rel=nofollow attribute. It was intended for use on blog comments, meaning, you wouldn’t be penalized for linking to potentially dodgy sites that a commenter used as their homepage in their comment.
Matt Cutts summed it up in a post a few months later:
The rel=”nofollow” attribute is an easy way for a website to tell search engines that the website can’t or doesn’t want to vouch for a link. The best-known use for nofollow is blog comment spam, but the mechanism is completely general. Nofollow is recommended anywhere that links can’t be vouched for. If your logs analysis program shows referrers as hyperlinks, I’d recommend using nofollow on those links. If you have a wiki that anyone on the web can edit, I’d recommend nofollow on those links until you can find a way to trust those links. In general, if you have an application that allows others to add links, web spammers will eventually find your pages and start annoying you.
It took all of about 1 minute for enterprising SEO’s to figure out new and exciting uses for the tag. Since Google didn’t count these links, you could now also control the outflow of PageRank from a page by the smart use of rel=nofollow, or sculpt internal flow of PageRank. In an interview with seoMoz, Google’s head spam cop said:
There’s no stigma to using nofollow, even on your own internal links; for Google, nofollow’ed links are dropped out of our link graph; we don’t even use such links for discovery. By the way, the nofollow meta tag does that same thing, but at a page level.
So everything was moving forward, rel=nofollow was in common use to cut down on passing “votes” to sites that the site owner was unsure of (as originally intended) and many sites also were using internal sculpting to tell Google and the others what pages were most important to them. Then, as is usually the case, some sites got carried away.
Then in June of 2009, Google announced that it had changed the way they processed the rel=nofollow tag. There are great detailed explanations of it from Danny Sullivan and Rand Fishkin, personally I love Danny’s comment under Matt Cutt’s post about the nofollow/sculpting change.
So now, using rel=nofollow can still make sense for what it was originally intended for, preventing comment spam, but that’s about it. PageRank now leaks through links even if they’re nofollowed, so some people have worried there will be less linking on sites that are PR obsessed. Although the search engines make you believe that nofollow’d links aren’t followed for discovery, there is evidence that they actually do follow them.
Yesterday, there was some news from Digg starting to no-follow untrusted links. The interesting part to me was that the Washington Post has the story. I never thought I would see the day where a major daily newspaper would be writing about Digg adding nofollow to it’s links. Has SEO finally gone mainstream?