When absolute positioning is used, something like top:auto creates a strange gap that I don't understand. It's probably OK by the spec (because the spec is necessarily vague for other reasons), but that doesn't mean it should be there. See the <P class="nine"> in the above URL and also, in http://www.fas.harvard.edu/~dbaron/csstest/sec090302c.html , examples of class nine, nineb, and nined (and currently more because bottom isn't working).

It also occurs on the left side in the P class="nine" in http://www.fas.harvard.edu/~dbaron/csstest/sec090302b.html

This is fixed now. That strange gap was because when the 'placeholder' frame's position was being translated back into the coordinate space of the containing block it was left relative to the containing block's border edge instead of the containing block's padding edge like it should be. So I added some code to translate by the containing block's 'border'

Verified fixed.