I would like to know about the policy of Google search engine because I find it to be very mysterious personally. I came across many such 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?

Google follows it's standard algorithm and procedure for calculating the page rank for the website. Google consistently scan the content of website and modify page rank according to the content in every two to four moths. Moreover google recently change it's algorithms for calculating page rank.

Hi,
Different search engines follow different policies to analyze a website and insert it in result pages.
I think, you have to emphasize more on the study and analysis of impact of Google's algorithms to improve rank in it.

well jessica said that very search engine has its own algos to determine page rank of any web site. You should go for getting back links of Good Page Ranked websites to get your Google page rank goal. Its is quie hard to get it but work hard will give you all that you want.

Its a long time since Google has updated its page rank toolbar, however don't get fooled by the green foolbar instead target SERP which will drive niche traffic and bring conversions

Hi,
Thanks for supporting my views. In addition, PR of the website updates three to four times in a year so I recommend you to put your efforts in increasing the SERP ranking and traffic to your site. This will generate business for your site.
To increase Page Rank of the website you can add relevant content to your site and increase the quality backlinks (from high PR sites, this will give the benefit of PR juice to your site).

Yes,differences of pr depend for ranking because high pr submission are improvement for any website.

You are right, but relevancy of the sites on which you are submitting your website's link also matters in the eyes of Google. So, be careful about relevancy and high Page Rank both, during submissions.