Alexa Rank is the indicator of the popularity of the resource according to the service Alexa (a subsidiary of Amazon.com).
Alexa collects information on the attendance of resources directly from users who have the toolbar installed Alexa Toolbar, which is formed on the basis of statistics about site traffic and lists of related links.
This is a disadvantage Alexa Rank, because the sample size is small audience – not every surfer is set in the Alexa Toolbar.
The algorithm of counting traffic ranking Alexa – average number of page views during the three months to the site. The lower Alexa Rank, the greater popularity of the resource. In addition to the indicator Alexa Rank, the service offers additional information about the site, which serves as a good tool for search engine optimization.
Subdomains can not be evaluated in isolation, but are Alexa Rank domain. Total traffic is calculated only for the top level domain.
Alexa Rank is a credible and meaningful measure of the sale of advertising on the resources (outside the headings in which this figure is practically not taken into account).