OStatic

Google Analytics (abbreviated GA) is a free service offered by Google that generates detailed statistics about the visitors to a website. Its main highlight is that a webmaster can optimize AdWords advertisement and marketing campaigns through the use of GA's analysis of where the visitors came from, how long they stayed on the website and their geographical position.

Unlike other server-side packages which analyze web logs, Google Analytics is a client-side tool that runs on the client-machines, enabling it to collect rich client-specific information like screen resolution from the client. However, it only collects information from clients that have javascript enabled. Therefore, it does not capture bot traffic information

Google Analytics is started by including JavaScript on each page the user wishes to track. This JavaScript loads larger files from the Google webserver and then sets variables with the user's account number. The GA report interface checks for the presence of this script on a tracked site's homepage, and warns should it not be available.

Many ad filtering programs and extensions (such as Adblock) can block the Urchin JavaScript. This potentially prevents some traffic and users from being tracked, and leads to holes in the statistical data. Also, privacy networks like Tor will mask the user's actual location and present inaccurate geographical data.

Some users do not have Javascript-enabled/capable browsers, which further limits the tracking ability of Urchin.