I had blogspot blog. To get more search engine visibility and traffic, I changed it to my dot com domain. The blogspot blog had PR2 rank. After customization to .com the rank fell to N/A. Now how I can retrieve the blog's old rank status. Help me.
You could insert new links at the bottom of your articles in blogspot to notify bots that your articles are now being published at the new domain.
What you've got to remember is that the published PR you can see is usually several months out of date, compared with the figures that Google is using itself - and PR plays a tiny, tiny part in the ranking algorithm. It's much more important to focus on where your site appears in the rankings and what you can do to move it up those rankings rather than worrying about the largely arbitrary and irrelevant published PR figure.
The concern of the page rank is coming when it is connecting to the online earning. Employers are demanding more PR sites for their jobs. A 100 word article gets different rewards depending on the site's page rank.