Jakob Nielsen’s Alertbox conducted a broad eye tracking study of user behavior across a wide variety of sites. Jacob Nilesen wrote:
“To investigate whether the “fold” continues to be relevant, I analyzed parts of the study with a total of 57,453 fixations (instances when users look at something on a page, typically for less than half a second).”
Key findings are:
Web users spend 80% of their time looking at information above the page fold. Although users do scroll, they allocate only 20% of their attention below the fold.
I recommend to read all about this study on Jacob Nielsen’s Alertbox.