An intermediary system operates as an intermediary between content servers and user devices, and provides services for determining page authority based on user browsing behavior. One such service involves receiving user browsing behavior from at least one browser on a user device and using the browsing behavior to assign an authority ranking to a content page (e.g., web page). The intermediary system can determine the content page authority based on explicit user authority rankings and/or implicit authority indications in page traffic data.