Embodiments include methods, apparatus, and systems associated with tracking display of digital content objects, and in particular digital content objects in delivered electronic messages. Digital content objects may be identified and associated with a digital content item. Digital content objects may be presented together in digital container. Different presentation layers containing one or more digital containers may be defined and transmitted in electronic messages. A digital content object tracking system may identify delivered and displayed digital content objects, and associate the display with digital content objects contained therein. The digital content object tracking system may compare displays or activations of one or more digital content objects with reference to co-displayed digital content objects. Other embodiments may be described and claimed.