Embodiments of a computer system, a method, and a computer-program product (e.g., software) for use with the computer system are described. These embodiments may be used to customize displayed content in a document, such as a web page or a user interface in a software application. In particular, by monitoring user activities while one or more users view the document during multiple sessions, the computer system can identify the most relevant content at a particular time. Then, the computer system selectively modifies the displayed content in the document based on the monitored user activity. For example, the computer system may selectively filter the content in the document so that a subset of the content is displayed. Moreover, the displayed content may be dynamically revised based on subsequent user actions.