Google Analytics is a free analytics solution that was designed to give you a complete view of every aspect of activity on your Web site. The most important detail in the installation process is making sure that your tracking code is correctly placed on every single page of your Web site.
Google Analytics allows you to not only track traffic that is coming to your Web site, but also track any traffic that may leave in the form of an external click.
You can also provide others with access to you Analytics account with full or restricted access.
Here is the link to Google Analytics: http://www.google.com/analytics/
