An experiment to show how designing for The Fold can be treacherous. Each line below is from a random sampling of past-visitors' viewport heights. Take care when making assumptions about people's screen sizes on the web.
Each line is a viewport from a previous visitor. Each line is slightly transparent, so the brighter portions are where there are multiple similar viewports. The lines are a 1000 long sample of the full dataset.
If you're interested in the full dataset, I wrote an article on my personal site that looks into the numbers a bit more deeply.
This is meant to show the diversity of viewports, not the popularity of them.