I want to know about the policy of Google search engine because personally I find it to be very mysterious. I came across many problems when I was working on improving the PR of my site. It would have been good if it had been determined regarding the high volume of traffic and the low competition keywords. Well, building backlinks helped me to gain PR5 in bing and yahoo. However, I am amazed not to find out the PR in Google. Can anyone tell me what the reason for such a difference is? Has Google recently modified its policy?