I don't beleive in this myth but i noticed it true for my one website which i started in early 2005 but i left working on it because i realised that it was a dumb idea. In few days i managed to get ~20 backlinks (not sure). After then i did nothing for that website. but in recent pr update it has gained pr 3 previously it was pr0 in all 2005 till first update of 2006 then it got pr1. i checked backlinks and it has only 2 live backlinks now. one from pr3 with 250 outbound links and one from p4 with 117 outbound links clearly showing that both are not quality backlinks. what's you comment about it?
PR is determined only by backlinks to your site. It has nothing to do with the age or quality of content. You can get a PR8 with a single link if the backlink is coming from a PR9 site (and your link is the only one of the page). A PR4 or less is fairly easy to obtain and one of your backlinks probably increased its PR, which increases the PR it passes to your site. Google only shows a fraction of your actual backlinks, so you also might have more backlinks passing PR than google is showing.
As you mentioned, you approximately got 20 links. Maybe Google is counting the other links also but not showing them in the backlinks. They could have helped in the PR also.
it was like more than one and half years back. now google displays only two backlinks that are listed in yahoo and appeared in tool checking. i am sure it has very few backlinks as shown by report because i left it incomplete and without any effort. question is why it stayed PR0 for about 1 year then it updated to PR1(not big deal) but now its PR3(though not high) but why its up? ...