Websiteoptimization.com today published the results of a user behaviour study which tracks what people do when they browser:
The Hamburg researchers also found an F-shaped pattern of clicking activity similar to results found in eye tracking studies.
[…] The researchers found that the nature of web navigation has changed over time. Comparing three web browsing studies ending in 1994, 1996, and 2005. […] The most significant changes were the increase in submit and new window events and the decrease in the use of the back button.
[…] Although all survey participants used a screen resolution of at least 1024 by 768 pixels, most did not utilize their entire screen for browser windows. Smaller windows, toolbars, and other widgets left users with about 160 horizontal pixels and 170 vertical pixels unused. For 1024 by 768 screen users, the average available document width was about 890 pixels
They also show something they call “heatmaps” which show the most active areas of mouseclicks (below, left graph) or eye movement (below, right graph, for google.com).