1. A computer-executable application embodied in a non-transitory medium for operation by a computer processor for implementing a method of testing visual elements in a rendered web page, the method comprising: defining, with the computer processor, a gold image at a first point within a web application; taking a screen shot of an actual image at the first point during execution of the web application with the computer processor; and comparing, with the computer processor, the gold image to the actual image and generating a difference image based on the comparison; wherein the difference image comprises: a first region highlighting a first difference between the gold image and the actual image within an area common to both images; and a second region highlighting a second difference between the gold image and the actual image which is not within an area common to both images.