In 1967, the Russian psychologist Alfred Lukyanovich Yarbus watched people as they looked at the same oil painting with different goals in mind. He noticed that the eye-gaze movements depended on the activity being performed and he concluded that people attended to those areas of the scene that were more likely to contain relevant information for the current task.
Our recent eyetracking studies build on Yarbus’s research, and reinforce the idea that tasks greatly impact user behavior on the web and therefore drastically change the outcome of eyetracking gazeplots and heatmaps. Better get the tasks right, or any eyetracking you do will be more misleading than helpful for driving your design.