A module may be included with a content item. The module may be configured such that the module performs a number of tasks at a first rate via a timer when the module is visible and at a second rate via a timer when the module is not visible. A script may be used with the module to determine the number of times the task has been executed by the module and to compare the number of times the task has been executed to a value. If the number of times that the task has been executed by the module is greater than the value then data may be output to indicate the that content item has been viewed. In some instances, the module may be used with a content item served in a cross-domain iframe.