launching firefox from terminal reveals Gtk-WARNING

firefox --new-tab http://www.ubuntu.com

(firefox:11065): Gtk-WARNING **: 07:40:00.389: Theme parsing error: gtk-widgets.css:3135:13: 'max-width' is not a valid property name

(firefox:11065): Gtk-WARNING **: 07:40:00.389: Theme parsing error: gtk-widgets.css:3136:14: 'max-height' is not a valid property name

This is fixable by removing the max-height and max-width lines from /usr/share/themes/Ambiant-MATE/gtk-3.0/gtk-widgets.css. Looking further a couple of other themes could use the fix too.

 $ for f in $(find . -name gtk-widgets.css); do grep -H "max-width" $f; done
./Ambiant-MATE/gtk-3.0/gtk-widgets.css: /* max-width: 15px;
./Ambiant-MATE-Dark/gtk-3.0/gtk-widgets.css: max-width: 15px;
./Radiant-MATE/gtk-3.0/gtk-widgets.css: max-width: 15px;