A system and method for determining client metadata using a dynamic rules engine is disclosed. The system may include a universal data agent, a site management tool, a targeting engine, an ad server, and a data warehouse. When a visitor visits a site on a content delivery system, the universal data agent and targeting engine may collect data about the visitor and site. The site management tool may configure the universal data agent and provided current rules for the dynamic rules engine. The collected data may be stored in the data warehouse and evaluated in the dynamic rules engine to produce a content category. The ad server may use the content category to serve targeted ads and/or other content to the visitor.