When resizing the Firefox window with Acid2 test open, the elements of the face move up and down. Build ID: Mozilla/5.0 (Windows; U; Windows NT 5.1; lt; rv:1.9a9pre) Gecko/2007100505 Minefield/3.0a9pre
This behavior is expected. See bug 289480 comment 128.
I'm going to reopen this; though one could argue whether it's a "bug", I think it ought to be fixed, and I've proposed a plan for doing that in bug 43114 (see also bug 19261); see those bugs for a description of the underlying problem that I think ought to be fixed.