Page Rank Sculpting
For a while Page Rank sculpting was becoming more and more the SEO's weapon of choice.
The most common form of Page Rank Sculpting came from the clever use of the no-follow link attribute.
Now , many of the articles online regarding this subject seem to either argue with each other or at best are a little confusing, and the truth is, page rank sculpting using no-follow is no-longer of much value. It seems the technique was misused (not necessarily in a bad way) and as ever Google quickly gets on top of things. So here I will give you at least an idea of what its all about but also explain why it is no longer much use.
(I actually recommend ignoring this technique altogether. This article is here not to give you an extra SEO technique but to make you aware of one that may waste a lot of time.)
A basic description. (How It Used To Be)
Lets say your home page has a PR of four and your home page links to 4 other pages on your site. The page rank from the home page is divided through the links so each page will receive a PR of 1.
If you then apply the no-follow attribute to 2 of your 4 links then these pages will not receive any page rank from your home page but the other two pages will now receive double - or so the story used to go.
Google has now changed the way the PR flows.
These days if you no-follow 2 links the remaining 2 links still get the same rank as they originally would have before. Not double. The really sinister part of this is that the no-follow links do take PR away from your other links but instead of it being channeled though it simply disappears. So now no-follow doesn't channel your PR - it burns it.
So, page rank sculpting was the art of making the PR flow around your site to the places you feel need it the most by keeping it away from the pages that don't need it.
The technique had most importance when looking at the pages you want to appear in the search engine results pages (SERP's)
If your site has 100 pages and 50 of them are information pages only relative to actual clients you may not want these pages to appear in the search engines. If you don't want them in the search engines then any page rank that flows through them is wasted.
In this case you would apply 'no-follow' to all the links that point to your client information pages to direct to PR juice to the pages you DO want in the search engines.
But no-follow doesn't work like that anymore. Using the no-follow MIGHT stop your private pages being indexed and this is still a good use but don't be fooled into thinking that page rank is now being evenly distributed to your other pages. It just simply dies.
(I say MIGHT because you have no control over the links that point to your site. Anyone can link to any of your pages and if they don't use the no-follow your pages can still easily rank.)
(For pages that you do want to keep out of the search engines I recommend using the robots txt file.)
So what's the point of no-follow then?
no-follow really does have a very good use. Lets say you have a shopping cart on your website. It would be a good idea to use no-follow on any links that directed a user to the checkout. After all do you really want a blank checkout page appearing on the search results? You also may not want your contact page appearing in the SERP's so no-follow all the links to your contact page. And so on and so on.
no-follow can be a great tool in keeping your content out of the search engine results but that's all it is. Its also useful if you wish to link to a bad site but don't want to pass any good PR onto it.
Google also recommends using no-follow on paid links. Google can and will penalise sites for too many paid links as its an old spam technique. No follow allows you to sell links from your site without being judged for Spam. Unfortunately by no-following paid links you also render them worthless as its the PR juice that people tend to pay for.
For a really in depth look at the no-follow tag and how it is applied now take a look at this article from Matt Cuts. He is the horses mouth of Google after all.