Firefox 3 comes with a handy-dandy built-in spell-checker. If you've ever used, say, Google Docs or posted a message in an online forum, you've probably seen it at work: A red line appears under each misspelled word. Right-click the word to see spelling suggestions (along with the usual context-menu options).
It's a great feature, but it has just one shortcoming: It doesn't work in Web forms. Well, not yet, anyway: It's a simple matter to tweak the spell-checker so it pulls form duty. Here's how:
1. Open Firefox, then type about:config in the address bar and hit Enter.
2. In the Filter box, type spellcheck.
3. Right-click layout.spellcheckDefault, and then click Modify. Raise the value from 1 to 2.
4. Restart Firefox.
Now the spell-checker should work in most online forms! If you're looking for another handy Firefox hack, check out Change the Speed of Mousewheel Scrolling.