Page Rank: A Quick Refresher
Most people with an interest in SEO (Search Engine Optimisation) are aware of Google's Page-Rank Algorithm.
The way page rank works is in essence very simple: each link from a page (page A) passes 'page rank' to the page it links to (Page B) ... the value of 'page rank' passed is the 'page rank' of page A divided by the number of links out from page A. The same then applies for Page B to Page C and so on.
The smarter of you will recognise that this is an iterative calculation (as the network effect means that Page Rank passed down will eventually be passed back in some form). The really smart amongst you may conclude this would be a non-convergent iteration; I believe that Google build in a 'decay factor' to prevent the problems that would ensue as a result. Of course the Page Rank calculation is in practice more complex still -- Google has algorithms and methods for determining the quality of links and pages which significantly refine the calculation.
Rel = "Nofollow": Google's Blindfold
Back in 2005/2007? Google adopted a policy whereby if the link from page A to Page B was given a Rel = "nofollow" attribute then Google would effectively ignore that link for Page Rank purposes.
The logic behind this move appears to have been somewhat confused. The intention was to allow websites to qualify outbound links to help Google (eg. to ignore paid links, advertisments, reciprocal links etc.); the actual outcome was for sites to suddenly start to 'nofollow' as many links as possible to preserve their page rank.
This is potentially catastrophic to Google's Page Rank algorithm: there are very few websites out there now that don't now 'nofollow' their outbound links (eg. Almost every forum, most blogs, Facebook, Twitter, You Tube etc.). If you want to check, go to a page with outbound links, right-click, 'view source', ctrl-f to find the link in the source code (use the anchor text of page URL as your search) and look for rel="nofollow" within the reference tag.
By trying to prevent people artificially boosting Page Rank, Google seem to have cut-off their main sources of 'natural linking' Page Rank. Your site may be being talked about on plenty of forums, people may be recommending you to their Blog readers ... but if the links are 'nofollow' google is blind to them.
So then in 2009 Google (quietly) let it be known that the Page Rank of the outbound page would still be diluted by the 'nofollow' links (so there is no Page Rank benefit to our 'Page A' of 'nofollow'ing outbound links; they still dilute the Page Rank passed by the nomal links) ... but that the receiving Page (our 'page B') would still not get any Page Rank benefit.
I guess the hope from Google is that people will be far more sparing in their use of nofollow tags as a result. Personally I greatly doubt it -- and even if this changes webmaster behaviour going forwards, google is poking its own eyes out if it continues to ignore the inbound Page Rank from nofollow links. Think about it: as it stands Google ignores sites that are being talked about on Forums, mentioned on Twitter, linked to from Facebook .... how can that be a good thing?
My personal view is that Google will quietly revoke the 'ignore nofollow' policy (if they haven't already) or see the quality of their search results decline (and allow the likes of Bing to make real in-roads).
It will also mean that new websites will find it far harder to build Page Rank (and therefore strong search engine results) than the embedded encumbents (who have links to their sites pre-dating the whole 'nofollow' wave). So not all bad then :0)
If you want to know more about this, you should read what Matt Cutts (the most public 'Google Guy') has to say; this blog entry of his (and the ensuing comments) is fascinating (if you like that sort of thing).
If you've read this and think "that's far too geeky and dull for me to care about" ... I hope that your businesses' and/or your personal success does not depend on your website(s) performing well in Google searches!