Technical Explanation

Unique Browsers (UB)
Each user visiting a site instrumented with the Nielsen//NetRatings code has a unique cookie id assigned to their browser to help determine browser uniqueness. This metric displays the number of Unique Browsers which visited a site owned by the publisher within the selected reporting period.

The Unique Browser is scaled; scaling this figure is to account for users who have cookies disabled.

Page Impressions (PI)
The total number of web pages successfully viewed within the selected reporting period.

A Page Impression is recorded each time a page instrumented with the Nielsen//NetRatings code is displayed in a browser window. This will occur whether the page is served directly from the web server, from a proxy, or from the browser’s cache.

This total includes impressions collected by the Java applet and by the CGI alternative for browsers that are not Java-capable or for which Java has been disabled.

Average User Session Duration (ASD)
A User Session reflects a period of user activity on a website, provided there is not more than 30 minutes’ inactivity between consecutive events for the same user. This report shows the average length of a User Session. This is calculated by dividing the total of the Page Durations by the total number of User Sessions.