Abstract: A user interface and methods are provided for presenting electronic content on a mobile device with a content-serving application. Heterogeneous content includes ‘internal’ and ‘external’ content. Internal content includes items served by a system hosting the application and/or other items to which the host has full access rights, while external content includes items to which the application host does not have full access rights (e.g., because they are served by a remote site). Placeholders representing content items are browsed using one input, and an item is opened by different input when its placeholder is displayed. External items may not be retrieved until they are opened. Gestures while an external item is open are communicated to its remote site, and when either type of item is fully panned left or right, the item begins to scroll out of view sideways and the placeholder of the next item scrolls into view.