NoFollow

Having links to your blog or website is important on the web. Not just because people may actually click on them and end up on your site. The mere presence of a backlink to your site by itself may increase your search result ranking (this is not the only parameter though!). And this simple fact is like pandorra's box...

Link spam
Some time ago I had created a website for a friend, very basic, very local, custom made. I had added a guest book (old school) and even though it was handcrafted it got picked up by spambots at some point in time, posting pages and pages of links and garbage. A simple captcha-like solution was enough to stop the madness. Captcha's indeed have conquered the web as a response to spambots and the like. But nowadays spamfighters have another weapon at their disposal..

rel=nofollow
By adding rel='nowfollow, to a link, as attribute inside the anchor tag (a-tag), a webmaster can prevent 'PageRank' attribution to this external link. The behavior is quite established amongst all major search engines. Whether the searchbot actually follows the link depends on the search engine. Note: Google nowadays does subtract the would-be pagerank from the total amount you can give away (ie other links on your site do get less as if there was no nofollow, but the nofollow link doesn't actually get it).

Why is this important?
Apart from being effective against spam(bots), the nofollow attribute is also important when you are seeking ways to (legitimately I presume) promote your own site. Since version 1.5 WordPress adds nofollow to all links in user-submitted content (ie comments headings and contents) by default. This may be relevant if you want to acquire links to your site by posting comments on other blogs (as is suggested in numerous videos and blogs elsewhere). Using the tool SEO Quake (which has plenty more features you may want to turn off for your own surfing convenience) you can quickly identify which links on a site actually have the nofollow attribute.

The future of the web?
It is interesting to think about where this is going. More and more sites and platforms are making use of nofollow, as backlink seekers' strategies evolve. Ultimately, this may at some point degrade the informative value of ranking algorithms because 'true' links are also removed from the equation. It is therefore not surprising that the amount of 'PageRank' is not the sole determinant of search rankings anymore. As more intelligent systems emerge, this ratio will most likely keep decreasing over time. What to do then, if you want to promote your website? Content, my friend, is King. Social media, my friend, the Queen.

PS:: this was, in hindsight, part three in an otherwise unintended series of html tags that play a role in search engine optimization :-D