How many links to get a Good PR?
Google Pagerank is still something we as webmasters and online marketeers are a little obssed about. The green bar stands for the popularity of your site according to Google.
Having a high PR rate will mean that Google will give your site a bit more love in the frequancy of visits and ranking for a certain keword can be easier.
I will not get into a discussion about relevancy because I do believe in highly target sites that cater a certain niche and when i talk about a niche i mean a specific small niche. Having links with related sites is much more valuable then having links from directories.
But in the linkbuilding quest having a link from a high pagerank site is better then from a low one. And altho you shouldn’t go only for high ranking the question that is aske a lot of times in the forums is how many links does it take to get a certain PR
…i do not say i know it exactly but it looks like the formula is someting like this
18 links from a certain pr will cause your site to have the same pr.
100 links from a certain pr (x) will cause your site to have a pr of x + 1
500 links from a pr x will have your site a pr of y +2
3000 links from a pr x = your pagerank will be x + 3
So if you get 3000 links from pr3 pages your pagerank will be 6 (3 +3)
This is only an indication and based upon my own experience, the google pagerank calculator and the graphs at tnx.net

