I am sorry - I did not pay much attention to your message. ui.SpellCheckerUnderlineStyle is used to correct a problem with Iceweasel not displaying the underline of misspelled words. If you have the underlines but your spell checker is not working, then you are having a different problem, probably connected to hunspell, but I can not say for sure. ui.SpellCheckerUnderlineStyle merely changes the way misspelled words are underlined