More and more of the media giants, such as Disney Media Networks and CBS, are investing millions of dollars on new research facilities to track how people respond to ads of varying sizes, locations and animations on the Internet.  We know how to measure precisely how often Web site visitors click on advertisements, and which kinds of ads draw the most clicks. But what about those who do not click, the many millions of others whose eyes merely flit across the screen?  These types of answers are what companies like Disney are hoping to uncover with these studies.  By using advanced technologies, such as eye-tracking goggles, heart-rate monitors, skin temperature readings and facial expressions (probes are attached to facial muscles), scientists and advertisers hope to uncover the secrets of how the human brain responds to different types of online ads and messages.  As findings are unveiled, they will begin to drive the design of Web sites and ad campaigns of the future.