These events are defined and documented in XUL docs but... a) onoverflowchanged is never fired, nor is it used in our tree. b) onoverflow is fired EVERY SINGLE TIME we reflow while overflow is in effect. c) onunderflow is fired when we reflow and it changes from overflow to underflow. I suggest that onoverflowchanged be removed completely. I also suggest that onoverflow be changed to fire only when we change from underflow to overflow. The only user of this in our tree is scrolling menus and it looks like they will continue to work with this change. This is really a XUL API change, so XUL documentation would have to be updated. Can someone tell me who to contact for that?