Hi guys,
It's free stats from
www.alexa.com It rates websites worldwide
They do a toolbar that you can download, that gives you ratings for sites.
A word of warning... this is not 100% accurate. The site has to be in their index to be rated, which not all are. Sometimes, keywords do not show up at all but it's useful (and free).
The Alexa score is a rough idea of visitors to a site. The lower the Alexa score, the better (I think Youtube is 3 or 4).
For cleaning sites, one million is pretty good, over say, twelve million is pretty crap. Some are twenty million plus (effectively, no visitors).