It's been said over and over and over again that the PR of your own site doesn't affect it's position in the SERPs, and yet I still come across people talking about how important PR is for your site. 
Since this topic still seems to be so misunderstood, let me give a short explanation of why the PR of your page doesn't matter for ranking in the SERP.
The only reason PR matters for your own site is if you're going to sell advertising space on your site or you plan to sell your site. Those are the only reasons you need to be concerned with the PR of your own pages.
For ranking in the SERPs, the PR of your own page doesn't matter, but the PR of pages you get backlinks from does.
Here's why:
But what about the PR of sites you get backlinks from?
Well, higher PR sites carry a little more weight than low PR sites. Lets say that for "keyword 1" you focused on high PR sites to get those backlinks. Now (depending on how many and how high the PR) those 10,000 backlinks on high PR sites will count the same as if you had gotten 30,000 backlinks on low PR sites. So by getting a lot of high PR sites backlinking for "keyword 1", your sites position in the SERP will be improved for that keyword.
To sum it up in short:
Since this topic still seems to be so misunderstood, let me give a short explanation of why the PR of your page doesn't matter for ranking in the SERP.
The only reason PR matters for your own site is if you're going to sell advertising space on your site or you plan to sell your site. Those are the only reasons you need to be concerned with the PR of your own pages.
For ranking in the SERPs, the PR of your own page doesn't matter, but the PR of pages you get backlinks from does.
Here's why:
PR
is based on the total backlinks a page is getting, but the SERP
position is based on how well your site ranks for a particular keyword.
So lets say your website "somedomain.com" has the following backlinks to it:
10,000 for "keyword 1"
10,000 for "keyword 2"
10,000 for "keyword 3"
10,000 for "keyword 4"
10,000 for "keyword 5"
Now the PR will be based on the total 50,000 backlinks, but it's position in the serp for any particular keyword will still be only 10,000 backlinks.
If you create another 50,000 backlinks for "keyword 6" then there will be a postive effect on the PR of the site, which now has a total 100,000 backlinks. But it won't affect it's position in the SERP for keywords 1 thru 5, (although "keyword 6" will now be ranking based on the new 50,000 links).
So that's why the PR of your own site doesn't matter as far as ranking in the SERPs.So lets say your website "somedomain.com" has the following backlinks to it:
10,000 for "keyword 1"
10,000 for "keyword 2"
10,000 for "keyword 3"
10,000 for "keyword 4"
10,000 for "keyword 5"
Now the PR will be based on the total 50,000 backlinks, but it's position in the serp for any particular keyword will still be only 10,000 backlinks.
If you create another 50,000 backlinks for "keyword 6" then there will be a postive effect on the PR of the site, which now has a total 100,000 backlinks. But it won't affect it's position in the SERP for keywords 1 thru 5, (although "keyword 6" will now be ranking based on the new 50,000 links).
But what about the PR of sites you get backlinks from?
Well, higher PR sites carry a little more weight than low PR sites. Lets say that for "keyword 1" you focused on high PR sites to get those backlinks. Now (depending on how many and how high the PR) those 10,000 backlinks on high PR sites will count the same as if you had gotten 30,000 backlinks on low PR sites. So by getting a lot of high PR sites backlinking for "keyword 1", your sites position in the SERP will be improved for that keyword.
- A page's PR is based on the total amount and quality of all it's backlinks.
- A page's SERP position is based only on the backlinks targeting a keyword.
