I upgraded to Lion when it first came out and the feature I like least is autocorrect. When typing, my Mac routinely corrects my spelling and often inserts incorrect words. How do I turn this feature off?
Helpful as I find autocorrect on my iOS devices—where typing is tricky because of a smaller keyboard with no physical feedback—I too find it distracting on my Mac. I can offer a couple of bits of welcome news for those who don’t care for this feature—not all applications support it and, for those that do, it can be turned off.
To do so, launch System Preferences and select the Language & Text preference. In that preference select the Text tab and disable the Correct Spelling Automatically option. Before you uncork the champagne and go on a tear of intentional misspelling, however, take note: Any applications currently open that support autocorrect will continue to correct your spelling and suggest words to you. To prevent them from doing this you must quit the applications. Relaunch them and autocorrect will be disabled.