A user's domain expertise may be estimated through several factors by monitoring different aspects of a user's interaction with a web browser. Based on the user's domain expertise, search results may be presented to the user that is commensurate with their expertise, resulting in a more efficient and productive on line session. A user's expertise in a knowledge domain may be determined from the user's behavior, including analyzing search queries, monitoring how the user navigates between and through websites, and analyzing the specific cites visited. As a user interacts with a browser, the user's estimated domain expertise may be updated and used to provide appropriate and useful search results. In many embodiments, a user may have different expertise levels for different technical domains.