After introducing the “nofollow” tag, other than for its intended use, many web masters used this tag to manipulate the link juice that was passing through the out-bound links of a particular page. We all know outbound links of a page are passing the link juice (PR value) from originating page to the target page.
In the following example original page has a total of 100 page rank value. This will be equally distributed among 4 out-going links, hence each carrying a value of 25 to its target page. (* assuming no decay factor)
If one of the above links is tagged with “nofollow” attribute, then the remaining 3 links will share 33 of PR value each.
This process of manipulating the PR that passes via out-going links is known as PageRank Sculpting/Link Sculpting. This was a very useful tactic as the target pages are benefiting with higher in-coming PR value while preventing PR values being transferred to unimportant pages.
However, after sometime Google changed their policy on the way they handle nofollow. Now, even though you use no follow tag, the remaining 3 links still will get only 25 each. And the link with the “nofollow” still doesn’t get any PR value. Which means 25 of PR value lost down the line.
To overcome this situation, webmasters have been using different tactics. The idea is to hide the link from the crawlers, so that they will see only 3 links in the page. But visitors still can see 4 links
Using redirects via Cgi-bin and blocking the cgi-bin directory via robot.txt file.
Using ifarmes to hide the links.
(Note 2 - PR Sculpting is not treated as a spam technique. Matt-Cutts of Google says “The notion of “PageRank sculpting” has always been a second- or third-order recommendation for us. I would recommend the first-order things to pay attention to are 1) making great content that will attract links in the first place, and 2) choosing a site architecture that makes your site usable/crawlable for humans and search engines alike.
Why Link Sculpting is Still Useful?
Link sculpting on all pages becomes important and useful when there are outgoing links to unimportant pages which you don’t expect to rank in the search engines. For example all footer links, shopping cart links, check-out links etc are actually leaking the PR value, hence depriving the other key pages making best use of the link juice coming from the original page. This is especially important for sites which have naturally attracted good PR value, due to their the domain age and any other initial link building and/or PR campaigns carried out. If category and/or product pages of these sites don’t have a good PR, it will be a good idea to use all opportunities to transfer the maximum PR value from home page to category/product pages. By letting the PR value to leak via footer & similar links, you may miss this opportunity.