Abstract: An online system receives advertisement (“ad”) requests for presentation to online system users. An ad request may include an identifier of a landing page identifying a source external to the online system from which content is retrieved and presented to a user who interacts with content from the ad request. The online system determines a quality score for the source based on a frequency with which online system users request content from the source via the online system and various types of interactions by online system users with content associated with the source that is presented by the online system (e.g., interactions with content associated with the source indicating user interest in the source). Based on the quality score for the source, the online system modifies a score for the ad request used by the online system to determine whether to present content form the ad request to a user.

Abstract: A social networking system presents a content feed including organic content items and sponsored content items to a user. To maintain user interaction with the content feed, the social networking system determines probabilities of the user performing various types of interactions with a sponsored content item and accounts for the determined probabilities when selecting content items for presentation via the content feed. For example, the social networking system generates a value for the sponsored content item based on the determined probabilities and determines a score for the sponsored content item based on the value and a bid amount associated with the sponsored content item. When selecting content for the content feed, the social networking system evaluates the sponsored content item based on its associated score. Prior interactions between the user and previously presented content may be used when determining the score for the sponsored content item.