What does PR4 stand for?

[Lunatic]

I'm new to blogging and have seen PR4, PR2, etc. used quite a bit. I know it has something to do with page rank, but what do the numbers stand for? And how do you find out what PR your blog is so you can give it a PR rating?

[DangerDave]

http://www.greenguysboard.com/board/showthread.php?t=21926&highlight=pr

[Lunatic]

http://www.greenguysboard.com/board/showthread.php?t=21926&highlight=pr
Thanks, great thread. I've got to remember to use the search function first. :)