A method, comprising: electronically crawling various digital content sources, by one or more servers, to identify and store, by the one or more servers, various digital content from the various digital content sources in a repository; identifying a set of the digital content that are responsive to a search query; detecting, by the one or more servers, an electronic tag within at least one portion of digital content in the set of digital content; automatically converting, by the one or more servers, the electronic tag to a frame element; generating, by the one or more servers, and transmitting, to a given user device that is remotely located relative to the one or more servers, a composite page that: is hosted at a different domain than at least some digital content in the set of the digital content; includes different digital content from the set of digital content that are identified and stored from the various multiple different digital content sources; and initially hides presentation of the frame element; receiving, by the one or more servers, an electronic request for additional content that was generated by the frame element and that identifies one of the various digital content sources; embedding, by the one or more servers and in response to the request, observation code into the additional content provided responsive to the electronic request; determining that the additional content was visually perceptible on a display of the given user device based on an electronic message received from the observation code executing at the given user device; and modifying a log based on the visual perception of the additional content with the digital content that was identified in the request. electronically crawling various digital content sources, by one or more servers, to identify and store, by the one or more servers, various digital content from the various digital content sources in a repository; identifying a set of the digital content that are responsive to a search query; detecting, by the one or more servers, an electronic tag within at least one portion of digital content in the set of digital content; automatically converting, by the one or more servers, the electronic tag to a frame element; generating, by the one or more servers, and transmitting, to a given user device that is remotely located relative to the one or more servers, a composite page that: is hosted at a different domain than at least some digital content in the set of the digital content; includes different digital content from the set of digital content that are identified and stored from the various multiple different digital content sources; and initially hides presentation of the frame element; is hosted at a different domain than at least some digital content in the set of the digital content; includes different digital content from the set of digital content that are identified and stored from the various multiple different digital content sources; and initially hides presentation of the frame element; receiving, by the one or more servers, an electronic request for additional content that was generated by the frame element and that identifies one of the various digital content sources; embedding, by the one or more servers and in response to the request, observation code into the additional content provided responsive to the electronic request; determining that the additional content was visually perceptible on a display of the given user device based on an electronic message received from the observation code executing at the given user device; and modifying a log based on the visual perception of the additional content with the digital content that was identified in the request.