At any time there may be sites that temporarily improve in the ranking. But if a site has constant traffic performance, it can be with the best ranking when the traffic data are added at the quarterly average. How are the most important sites calculated? The list of the most important sites is based on changes in average reach (number of users). For each site in the network, it is estimated the average weekly reach and compares with the average reach during previous weeks. Among most significant sea change, highest site will be placed on the list. The change in the percentage that appears in the list of the most important is based on the change of scope.
It is important to note that the ranking of traffic displayed on the page of the most important sites are the weekly traffic rankings. These rankings are not the same as the ranking of traffic averaged in three months, which are shown in other Alexa services, and are not the same as the reach numbers used to generate the list. Some important notices for the traffic data are based on the set of toolbars that use Alexa. These data may not be a representative sample of the global Internet population. To the extent that our population of Alexa users differs from all Internet users, their estimates of traffic can give greater importance or dismiss the current traffic to any website in particular. In some cases traffic data may also be negatively affected by the site definitions.
With tens of millions of accommodations on the Internet, its automated procedures to determine what accommodations are serving the same content may be incorrect and/or out-of-date. Similarly, the determinations of domains and homepages are not always exact. Sites with low traffic will not be ranked properly by Alexa. For Alexa data come from a large population of users who use the toolbar of this portal and other sources that provide traffic data. However, the size of the Web and the concentration of users in sites most popular makes it difficult to correctly determine the ranking of Web sites that receive less than 1,000 visitors per month.Generally, the rankings of 100,000 and more should be considered as reliable. On the contrary, more approaching a site position #1, more reliable its traffic ranking will be.