Behold, the Fold

The bottom of your screen may be very different than the bottom of my screen. With thousands of devices in use and all with vastly different resolution, there is no way to predict where the bottom of a viewport will fall...

We should design pages with the assumption that users are going to start at the top and work their way down, so the most important things should be at the top. The design and layout should encourage visitors to want to learn more as they move down a page.