1. A computer-implemented method for tracking user interactions with a mobile user interface (UI), the method comprising: collecting data while a user interacts with the mobile UI through a touchscreen, wherein the collected data includes tap-attempt data that specifies coordinates for touchscreen locations that the user has tapped while interacting with the mobile UI; examining the tap-attempt data to identify a cluster of tap attempts that are proximate to a non-tappable element in the mobile UI; and when such a cluster is identified, notifying a UI designer about the cluster of tap attempts that are proximate to the non-tappable element, to enable the UI designer to make adjustments to the mobile U.