Firefox 2 users may have noticed that the built-in spell checker does not automatically check single-line text fields, such as Google.com. Instead, you need to open the context menu (right-click), and choose
Spell check this field. With multi-line text fields (for example, the
Detailed Comments box at hendrix.mozilla.org), the spell checker is automatically turned on.
To get the spell checker to automatically check all text fields, enter about:config in the address bar. In the resulting page, search for the preference layout.spellcheckDefault.
Double-click on it, and change the value to 2.