> May I know PR is referring to Page Ranking or different thing?
It stands for "PageRank", a value that Google calculates for each page
and uses in the ranking process. Read all about it at
http://en.wikipedia.org/wiki/PageRank , or one of the other links at
http://www.google.com/search?q=pagerank
> I found
> in one of the question they stated their web page has PR0 and some
> with PR4, what is this about?
Google don't release the exact PageRank value for each page, but every
three months or so they publish an approximation via the Google
toolbar (of which more later). This is a scale from 0 to 10, the
higher the better.
> Anyone can advice me where I can check our web page ranking? Any
> reliable source that I can check?
You can get the Google Toolbar from
http://toolbar.google.com , or
install a Firefox plug-in like Search Status, or find the PR online at
a site like
http://www.prchecker.info . All are equally (un)reliable
as they return the approximate, up-to-three-months-old toolbar PR
value.
Frankly, while it's nice to have a good PR value, I wouldn't obsess
about it too much.