PUBLIC MARKS with tags visible & jQuery

jQuery.fracs determines the fraction of an HTML element that is currently in the viewport, as well as the fraction it takes of the complete viewport and the fraction of the area that might possibly be visible. It also provides the coordinates of the visible rectangle in document, element and viewport space. See the demo to get an impression of some of the features.

On a project I worked with Paul Irish on recently we found that we needed to asset whether an element was visible, but the :visible selector doesn't always do the job.