What makes a Firefox window change size during startup?

[jis]

Bug report 228114 (https://bugs.launchpad.net/ubuntu/+source/firefox-3.0/+bug/228114) gives an impression Firefox window size may change during session startup. Firefox session is started as part of Xfce session. Title bar is drawn by different size information than the rest of the window. What might cause this inconsistency?

[mali2297]

Is the window set to maximize?

[jis]

I use to use Firefox windows maximized.

[mali2297]

I use to use Firefox windows maximized.

Then try instead to adjust the window size manually. I think there is an inconsistency because both Firefox and the window manager wants to set the window size.