[whatwg] mouseout Event

[WeBMartians]

Fumbling around in the document, I came across the description of when the mouseout event is bubbled. What I did not see is anything about mouseouts after mousedowns but before mouseups. I understand why such text is missing - the combinations are nearly astronomical. However, I tried the following:
	<img ... onmousedown="this.src='down.gif';" onmouseout="this.src='out.gif';" onmouseup="this.src='up.gif';" ...
Firefox2 (Windows) reports the mouseout only if it is not immediately preceded by a mousedown.
IE7 produces/handles the mouseout event whether or not a mousedown has occurred.
I have not tried Opera or Safari.

Am I having yet another case of "male pattern blindness" (as my spouse calls it) and there is text specifying that successive mouse (and keyboard) events are to be handled? Or is there no such text and adding would it be a task of such magnitude that WHATWG should not even try?