From time to time, you may encounter words you use on the Web that do not appear in the dictionary, but should not be corrected by Firefox’s spell checker. These could be names of places, songs, software, etc… Web 2.0 companies with goofy names are frequently flagged as having been spelled incorrectly. Telling Firefox’s spell checker to ignore these words takes two clicks of your mouse.
The next time you type a word that Firefox incorrectly flags are a misspelling, right-click on the word and click on “Add to Dictionary”. If you are on a Mac and use a one-button mouse, hold CTRL and click on the word. Once the word is in your dictionary, Firefox will no longer complain about it.
Here is a screenshot:
