height as a percentage of the body element in CSS

[John Fitzgibbon]

Hi,

In CSS, when the height attribute of an element is expressed as a percentage, the percentage in question is a percentage of the height of the parent element. In many cases, the parent element will be the body element.

Is the height of the body element the height of the viewport (or screen) or is it the height of the document? A document may run to two or three screens. Any testing I have done suggests it is the screen. It is easier for me to manage if it is the screen but I haven't seen this written down anywhere. It is not in 'Cascading Style Sheets: the definitive guide' by Eric A. Meyer. My worry is that there is a third possibility which I have not considered.

Regards
John
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