This box is 4000 pixels tall so that that total page height is more than the visible height.
There are 16 coloured boxes with their positions obtained in different ways. Each set of four looks at scrollHeight, Height, clientHeight and innerHeight. The first set of four (reds) accesses these through document.getElementByID. The second set uses document, the third document.body and the fourth document.documentElement.

This box is 200px in height + 100 from top = 300px total usage.