Those who work in the professional field of web development know all about heat maps. They're a way of visualising precisely how someone looks at a web page. Given the right equipment, you can generate these heat maps by tracking a visitor's eye movements. Without such kit, you can generate very useful and fascinating heatmaps by tracking mouse movements.
If you run a web site and you want to see just how easy it can be to generate and view heatmaps, check out Hotjar at www.hotjar.com. It's a commercial service, also available in a basic free edition, that generates heat maps for your web site! Just sign up for a free account, and then place the tracking code that it generates (a short script file) into the header section of any pages that you want to track. Now just wait a while, then log into your Hotjar account to view the heat maps, and even to view recordings of visitors' mouse movements within your tracked pages.
It's a fascinating way to study how people use your web site, and to learn where best to place those "must-see" items on the page.