tedster - 3:20 am on Jun 29, 2010 (gmt 0)
it won't be retained on the page with the no follow'ed links either.
That makes it sound like links lower a page's PR, and that's not exactly the way I understand it. If you have a page and add a link to it, the totla page Rank does not go down. But there is a complex situation involved and some people online have been using language that makes it sound liek that happens.
Here's how I understand it. A page has an amount of PR - and its "vote" for another page through a link, carries a share of that total PR. But that weight calculation is a way of giving a certain value to the vote. The fact that there's a vote, in itself, doesn't subtract any PR from the original page.
It actually gets a bit more complex, because the "votes" keep on going around the web. So some of the weight eventually gets passed back to the page through backlinks - and this happens over and over. but with each step, the power of a vote gets dampened a bit, so that after a while, instead of growing off to infinity, the total PR of any URL settles down to a limit.
So the change in nofollow calculation means that the other links pon the apge are not voting any "more" PR just because a nofollow exists. And in that way, slightly less PR (just a tiny sliver, really) is being voted around and around in that continuing, "iterated" calculation.