Reference:
The percentage is calculated with respect to the height of the generated box's containing block.
coming from CSS 2.1, section 10.5 Content height: the 'height' property

Firefox 3.0.4, Opera 10.00 alpha 1, Safari 3.2, Konqueror 4.1.1, NS 7.2, K-meleon 1.x, Seamonkey 2.x all pass both of these tests.

Update: This bug has been FIXED in Internet Explorer 8 RC1 (build 6001.18372) released on January 26th 2009. Otherwise, Internet Explorer 8 RC1 PASSES this specific and particular testcase.