<a rel="nofollow" href="http://www.example.com/page.html" >Visit My Page</a>

...an indexing command first implemented 2 years ago in 2005. Its purpose is to flag that a link has not been explicitly approved by the site owner, and as a result the search engines treat the link as having low/no trust or value in relation to the site it is posted on. It was a response to sites being spammed with irrelevant links e.g:

• You have a site with a forum
• Comments posted to the forum are full of links to utter rubbish (the usual suspects- casinos, porn, drugs, etc.
• This comment spam leads the search engines to devalue your site in light in of the dross it is associated with

All in all a good thing- you'd think so wouldn't you? But what happens when you get creative with your nofollow and try to use it as way of bumping up the value of your internal links?

The idea is that by applying a nofollow to selected internal links (i.e. your regular site assets- about us, privacy policy, trackback URLs, comment RSS feeds etc.) none of your precious link juice gets squandered. It is thought that in this way PageRank can be preserved for pages that you see as more important.

Google's Matt Cutts says that the nofollow attribute is just a mechanism that gives webmasters the ability to modify PageRank flow. Other mechanisms (e.g. a "disallow page" in robots.txt, or an on-page noindex meta tag) would also work but nofollow is simpler. Apparently Google are agnostic about how you modify your PageRank flow, so nofollow is 'safe' to use.

...except some people disagree, vehemently. One comment I found was explicit, "There is no need to use nofollow on internal links", they went on to say that Google sees those asset pages as a sign of quality and trust. The theory is that by nofollow'ing your own links you may slow down indexing, and remove trust signal pages. This is speculation though, and has yet to be conclusively proved.

One thing is true, nofollow prevents low value pages getting link juice, which means that when you build a new site you are able to control which content does get it. Not bad for a 2 year old.