This is a simple jQuery plugin that makes it easy to track the visibility of a set of elements on page. In this context, we are not referring to the HTML visible attribute. Instead what this tracks is how elements go in and out of the viewport as a user scrolls up and down a page. As the user scrolls down the page, a given element will become partially viewable, then fully viewable, then partially viewable again, and finally is no longer visible.

View the VisibilityTracker website for more information or to download.