A third party system includes a tracking mechanism in various content provided by the third party system. When a client device presents content provided by the third party system, the client device executes tracking mechanism, causing the client device to communicate information identifying the content, identifying a user associated with the online system, and other information to the online system. Based on the information received from the client device, the online system selects a rule from rules provided to the online system by the third party system. The online system then performs an action included in the selected rule, allowing the advertiser to initiate various actions by the online system while including a common tracking mechanism in different content provided by the third party system.