A new eyetracking study found user's main reading behavior was fairly consistent across many different sites and tasks. The dominant reading pattern looks like an F and has the following three components:
Users first read in a horizontal movement, usually across the upper part of the content area. This initial element forms the F's top bar.
Next, users move down the page a bit and then read across in a second horizontal movement that typically covers a shorter area than the previous movement. This additional element forms the F's lower bar.
Finally, users scan the content's left side in a vertical movement. Sometimes this is a fairly slow and systematic scan that appears as a solid stripe on an eyetracking heatmap. Other times users move faster, creating a spottier heatmap. This last element forms the F's stem.