[參考鏈接][https://support.mozilla.org/en-US/kb/how-do-i-use-firefox-spell-checker]

Disabling automatic spell-checking

1. By default, Firefox is configured to automatically check spelling. You can turn it off in the Preferences window:

2. Click the menu button
   

   New Fx Menu

   and choose Preferences.

3. Select the Advanced panel.

4. Click the General tab.

5. Uncheck Check my spelling as I type.

   

   Spell Checker Pref 38

6. Close the about:preferences page. Any changes you've made will automatically be saved.