Web Analytics:
Web analytics is the study of the behavior of website visitors. From business point view this technique is used for determining which page or which portion of the site is attracting more and more people.

Data collected from this contains different type of report like visitors per day, New visitors, visitor is from which part (country, continent) of the world, Bounce rate etc. These reports are used for improving the site and hence marketing campaign.

Web analytics technologies
Mainly two techniques are used for collecting data.

1. Web server log file analysis
As web server records all their transaction in a log file. This log file can be analyzed and can provide data on various aspects of the site traffic. This was the point from where Web Log Analysis Software was developed. First commercial Log Analyzer was released in 1994.
Two units of measuring a site were discovered. These were Page views and Visits (Session). Page View was defined as a request made to the web server for a page. While visit was defined as sequence of requests from a uniquely identifies client.

2.Page tagging
Concerns about the accuracy of logfile while caching led to second method called Page Tagging or Web Bugs.
In the 1990s Website counters were common. It is simply an image showing the number of times the page/site had been requested. Subsequently trend started to have an invisible image instead of having a visible one. So this can send information to third party Web Analytics Company and statistics can be generated. Third party service also manages the process of assigning a cookie to user which can uniquely identify them during their visits.
With the popularity of Ajax based solutions, an alternative is came up. Which is to implement a call back to server from the rendered page. In this case when page is rendered by on the web server a piece of Ajax code would make a call back to server to pass information that can be then aggregated by a Web Analytics company.