Is it possible to use Mozillas spellchecker to check the spelling in textarea fields (e.g. when entering text on a message board)?
Not by default, but if you install this Extension, you can. Please note that I have linked directly to the extension installer. Click on “Install” if you wish to install it, otherwise click on “Cancel”. If you want to install it for all Mozilla users/profiles click on “OK”, if you just want to install it for the profile you are currently using click on “Cancel” when prompted.