In the following test case there is a float (green) followed by a box with clear (red). The box contains another float (aqua). In IE8b1 the second float escapes out of its box, going to the side of the first one. This is not correct: according to the CSS spec: A floating box's outer top may not be higher than the top of its containing block.

A left float
Another float inside a box with clear

The problem does not occur if the containing block of the second float has any non zero padding or border.

A left float
Another float inside a box with clear and top border
A left float
Another float inside a box with clear and top padding
A left float
Another float inside a box with clear and top margin

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