1. A data processing computer system for customizing a presentation comprising: a bus; a communications unit connected to the bus; a storage device connected to the bus, wherein the storage device stores program code; and a processor unit connected to the bus, wherein the processor unit is configured to run the program code to: share a content displayed on a source computer system with a set of target computer systems, wherein the content is displayed on a target display on each target computer system in the set of target computer systems; responsive to a change in the content displayed on the source computer system, identify a progress in displaying the change in the content on the target display on the each target computer system in the set of target computer systems, wherein the change in the content displayed on the source computer system is a difference between the content displayed at a current time as compared to the content displayed at a previous time, and wherein the each target computer system receives, and begins to display, the change in the content on a respective target display; generate an indication of the progress since beginning to display the change in the content until the change in the content is actually displayed as complete on the target display on the each target computer system in the set of target computer systems at the source computer system, wherein the progress in displaying the change in the content on the target display for the each target computer system is monitored and compared with the progress in displaying the change in the content of each other target computer system in the set of target computer systems; and display the indication of the progress in displaying the change in the content on the target display on the each target computer system in the set of target computer systems on a source display on the source computer system.