An online system accesses a content item containing a link to an external landing page. When an opportunity to present content to a viewing user occurs, the system determines a quality metric for the content item. The system further determines, based on the attributes of the external page, a quality metric for the external page. The quality metric for the external page is adjusted based on the quality metric of the content item. The system computes a value score for the content item based on the quality metrics for the content item and the external page. The content item is ranked against other content items for presentation in the opportunity. Content items are selected by the system and sent for presentation to the viewing user.