Small colored moving patterns irresistibly attract our visual system. This is enough to explain the hypnotic power of TV. Animated banners or icons produce chaotic eye movements by capturing attention. Results from an experiment called the antisaccade task, show that young and slow readers are particularly sensitive to such kinds of visual distraction. An option to freeze this invading visual harassment is a must for a readable Web browser.
Font aliasing and screen flicker are the two important factors that lower efficiency when reading from screens. Font aliasing is because the edges of characters are not smooth but step-like. Flicker is due to the fact that the screen is refreshed about one hundred times per second. Though not perceived consciously, the added noise generally penalizes reading. Tiny and fast eye movements occur during fixation. This so called tremor has a magnitude of less than the thickness of a character line and a frequency of 100 cycles per second. Tremor is used to analyze the outline of objects and to refresh the output of the eye detector cells. Current screen and antialiasing technologies have still to improve as the eyes notice flickering up to 400 Hz.