Alexa's traffic rankings are based on the usage patterns of Alexa Toolbar users and data collected from other, diverse sources over a rolling 3 month period. A site's ranking is based on a combined measure of reach and pageviews. Reach is determined by the number of unique Alexa users who visit a site on a given day. Pageviews are the total number of Alexa user URL requests for a site. However, multiple requests for the same URL on the same day by the same user are counted as a single pageview. The site with the highest combination of users and pageviews is ranked #1.
Alexa's traffic rankings are for top level domains only (e.g. domain.com). We do not provide separate rankings for subpages within a domain (e.g. http://www.domain.com/subpage.html) or subdomains (e.g. subdomain.domain.com) unless we are able to automatically identify them as personal home pages or blogs, like those hosted on Geocities and Tripod. If a site is identified as a personal home page or blog, its traffic ranking will have an asterisk (*) next to it: Personal Page Avg. Traffic Rank: 3,456*. Personal pages are ranked on the same scale as a regular domain, so a personal page ranked 3,456* is the 3,456th most popular page among Alexa users.