Anonymous web browsing is browsing the World Wide Web while hiding the user's IP address and any other personally identifiable information from the websites that one is visiting. Anonymous web browsing is generally useful to internet users who want to ensure that their sessions can not be monitored. For instance, it is used to circumvent traffic monitoring by organizations which want to find out or control which web sites employees visit.
From : http://en.wikipedia.org/wiki/Anonymous_web_browsing