google analytics
Google Analytics is a free service offered by Google that generates detailed statistics about the visitors to a website. Its main highlight is that the product is aimed at marketers as opposed to webmasters and technologists from which the industry of web analytics originally grew. It is the most widely used website statistics service, currently in use at around 40% of the 10,000 most popular websites.
Google Analytics can track visitors from all referrers, including search engines, display advertising, pay-per-click networks, email marketing and digital collateral such as links within PDF documents.
Integrated with AdWords, users can review online campaigns by tracking landing page quality and conversions (goals). Goals might include sales, lead generation, viewing a specific page, or downloading a particular file. These can also be monetized. By using Google Analytics , marketers can determine which ads are performing, and which are not, providing the information to optimise or cull campaigns.