I'm planning to buy domain here in DP and I want to if how will I validate if a domain has a valid PR or not? Thanks!
simplest way is go to google.com type info:yourdomainame When the search result shown the same domain name you have input, it means that the PR is valid but in case it is different it means that the real PR belongs to that site in the search result.
Step 1: Check PR using DigPagerank or CheckPagerank; and Step 2: Double check the validity using Google. Type "info: domain" All the best!
the pagerank checker would be be worked sometimes, try to Google search and check the backlink to know what and how many sites has pointed to this domain.