id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
6941	horizontal scrollbar in firefox	Holger Hees		"which only occurs in the initialization for 1 second to and is dependent on their parents' style

you need to change

_source/plugins/wysiwygarea/plugin.js line 537

from

element.setStyles( { position : 'absolute', top : '-3000px' } );

to

element.setStyles( { position : 'absolute', left: '-3000px', top : '-3000px' } );"	Bug	closed	Normal		General	3.5	fixed	Firefox HasPatch	Sa'ar Zac Elias