People think about PageRank in lots of different ways. People have compared PageRank to a “random surfer” model in which PageRank is the probability that a random surfer clicking on links lands on a page. Other people think of the web as an link matrix in which the value at position (i,j) indicates the presence of links from page i to page j. In that case, PageRank corresponds to the principal eigenvector of that normalized link matrix.

Q: Does this mean “PageRank sculpting” (trying to change how PageRank flows within your site using e.g. nofollow) is a bad idea?
A: I wouldn’t recommend it, because it isn’t the most effective way to utilize your PageRank. In general, I would let PageRank flow freely within your site. 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.

For example, it makes a much bigger difference to make sure that people (and bots) can reach the pages on your site by clicking links than it ever did to sculpt PageRank. If you run an e-commerce site, another example of good site architecture would be putting products front-and-center on your web site vs. burying them deep within your site so that visitors and search engines have to click on many links to get to your products.

There may be a miniscule number of pages (such as links to a shopping cart or to a login page) that I might add nofollow on, just because those pages are different for every user and they aren’t that helpful to show up in search engines. But in general, I wouldn’t recommend PageRank sculpting.

Read the full post