Open two Mozilla windows. Position the next to each other one on the right of the other. In one of the windows, open a modal dialog box. Click on the other Mozilla window while the modal dialog box is open. Focus switches to the other Mozilla window as expected. Now use the mouse to drag the second Mozilla window over the first Mozilla window. You'll notice that the modal dialog box from the first window appears to remain above the second Mozilla window. This modal dialog box should remain above the Mozilla window that spawned it, but it should be coverable by any other Mozilla windows.

Modal windows are supposed to stay on top -- the bug is that you shouldn't be able to switch the focus. (That bug already has been written.)

verified.