1)  Total number of site visitors (actual people) viewing a given site on a daily, weekly, monthly or yearly basis.  This statistic is important because it measures the number of "eyeballs" viewing a given site during a given time period.

2)  Total number of page views (one page viewed by one site visitor equals one page view) logged by a given site on a daily, weekly, monthly or yearly basis.  This statistic is important because it reveals

a)  how interested site visitors are in the site being measured - the more pages viewed on average per visitor, the more "engaged" users are with the given site

b)  how much advertising space is available for purchase

3)  Repeat Visitors (as the term implies, persons who visit a given site more than once) provide a measurement of user retention, user loyalty and long-term interest in a given site.  The higher the ratio of repeat visitors:

a)  the better the site is positioned in what is now termed the "Web 2.0" (social networking) world

b)  the more likely an advertiser is to reach the demographic that the repeat users represent.

While each measurement is important in and of itself, by taking all three measurements into account, a more accurate and broad-based perspective on site popularity is attained.

Ranking.Com measures popularity based on all three measurements above.  Thus, the popularity ranking for Yellowstone Net (ranked as the 5,877th most popular web property worldwide, as of August 2008) is a combination of all three measurements. 

Other market research firms which specialize in online traffic have their own formulas which result in different rankings.  Quantcast, for example, ranked Yellowstone Net as the 17,069th most popular web property in August 2008.