Ok PR ( Page Rank ) though many people might say PR is not all that important and all. The first thing that one will do if they want to buy an advertisement is check the PR. Usually the higher your page rank is the more you can charge for advertising space on your site or the site itself if you want to sell the site. Many webmasters are also buying dofollow text links for their website from high PR websites. So that is the initiative required for the scammers to fake their Page Ranks.

Now lets look @ how we can identify a webpage that is faking its page rank.

1) Using 3rd Party Sites
There are sites which scans a webpage to see if the page ranks is valid or not, 2 such examples are

http://www.checkpagerank.net/
http://www.rankchecker.com/links/

2) Backlinks
Say a website is having a Page Rank of 8 and only 10 back links , most likely the webpage ranks has been fabricated ( unless of-course his link backs are from PR9 and 10 sites ).
If you have the google toolbar installed you can check backlinks by right clicking on the page Page Info > Backward Links or search for link: domainname.com in both google and yahoo( a bit more accurate to search for backlinks )

There might be cases where a domain ( say site A ) is redirect to a higher PR site ( site B ). The masked page will temporarily gain the pagerank of the page it was masked to. All a scammer has to do in order to fake a pagerank is use a redirect for their domain and point it to a high pagerank domain, so If they point the site to facebook for a while they have PR 9 ( it will stay @ PR for a while even after the redirect is removed ). And the worst kind are the site which uses cloaking ( what they do is they send search engine spiders to high PR sites , while normal visitors are sent to their site ). Now lets check how we can sniff this one out

3) Redirected PR detection
easy way to check this is type in info:sitename.com, it will usually return one result and the result will be of that domain ( may be with www or without it ) if its pointing to something else its usually a fake PR site.

4) Check header info for redirect
We can check a sites header info to see if they are using 301 - Permanent Redirect , 302 - Temporary Redirect or Cloaking. Try this site to check the header information :

http://webtools.live2support.com/header.php

When we try to look @ the header info for the fake Pr site its got a HTTP request ok/completed code of 200
which means the site is not redirecting but using the cloaking technique. Just verify the sites google cache by using cache: site.com if its got invalid info thats not related to the site you were searching for , then the PR might be a fabricated one.