aakk9999 - 3:08 am on Mar 15, 2010 (gmt 0)

Ask why low PR pages outrank higher PR pages about the same topic.

I think one of reasons is because if you ONLY take focused on-topic PR juice, the low ranking PR page may actually have a stronger "on-topic" PR than the high ranking PR page (where on high-ranking PR page the majority of PR may come from wider or perhaps more general on-topic subject).

So PR may tell you how popular the page is, but it does not tell you what for.

I would also argue that the more niche the query is, the more chance of lower PR pages to outrank high PR pages, whereas for more generic queries is more chance for high ranking PR pages to outrank lower ranking PR pages.