What is Alexa Traffic Rank?
In simple terms, Alexa Traffic Rank is a rough measure of a website's popularity, compared with all of the other sites on the internet, taking into account both the number of visitors and the number of pages viewed on each visit.
The global traffic rank is a measure of how a website is doing relative to all other sites on the web over the past three months. Alexa collects traffic data on a daily basis from millions of users who have installed the Alexa toolbar, and other sources, and then uses a complex mathematical formula on three months' worth of data to arrive at the ranking for each site.
This can be interpreted as the website's position in a massive league table based on both visitor numbers and the number of pages viewed by each visitor. The 'most popular' site is given a rank of 1, the second 'most popular' a rank of 2, and so on down to the millions of websites that receive relatively few visitors.
A website is typically defined at the domain level. For example, www.yahoo.com, omg.yahoo.com and news.yahoo.com are all treated as part of the same site, because they all reside on the same domain, yahoo.com. Exceptions are made for personal home pages and other hosted sites, for example beekeepers-cooperative.blogspot.com, which are treated as separate sites.
You should bear in mind that the rankings are calculated using traffic data collected only from users who have the Alexa toolbar installed, and who may or may not be a representative sample of all those who use the internet.
As a result the number of visitors to each website may not be accurately estimated, especially where that site receives relatively few visitors. In general, traffic rankings of more than 100,000 should not be considered reliable, but used as a rough guide only.