How is padding-top as a percentage related to the parent's width?

Question

Here is an example:

http://jsfiddle.net/QZAd8/1/

Notice how all of the red divs are the same height and have padding-top:100%;, yet

Answer 1

It's true that padding percentage is relative to the width, but specifically, padding: 100% can also be read as padding: *width-of-container*px.

The A and C blocks had a width of 70px. Applying padding: 100% was the same as padding: 70px