Over deze add-on
Norwegian bokmål and nynorsk dictionaries for Mozilla Firefox, Mozilla Thunderbird and SeaMonkey.
Note: This is a dictonary for the built-in spellchecker and not a dictonary used for translation. This extension is put in the Dictionary section so that it could be included on the Dictionaries & Language Packs page. (https://addons.mozilla.org/en-US/firefox/browse/type:3).
(It used to be available on that page, but it's not there now since this extension has been splittet into two different extensions, one for the Norwegian bokmål dictionary and one for the Norwegian nynorsk dictionary).
These dictionaries is based on the Spell-norwegian project available at http://no.speling.org/, and it's the same dictionary used in e.g. OpenOffice.org and some other OpenSource projects.