We are building a new kind of agent that acts as a user's assistant in browsing the World Wide Web. Many current Web tools perform searches for the user, but our approach is to consider the search for information as a cooperative venture between the human user and an intelligent software agent. Rather than search a pre-indexed portion of the Web according to user-stated keywords, the agent, Letizia, infers interest implicitly from observing user actions and tries to stay just a few steps ahead of the user, searching the user's immediately accessible links dynamically.