Quite possibly the best thing about Firefox 2.0 is its spell checking abilities.  However, by default, it only automatically spell checks textareas (text boxes with multiple lines) and not text inputs (single line).  By right-clicking on a text-input, you can select "Spell check this field", but I wanted something more permanent.  Here it is:  Go to about:config, search for "layout.spellcheckDefault" and set the value to "2".