So here we are in the era of Word’s red-underline “wrong spelling, dumb ass” feature and Outlook’s Always Check Spelling Before Sending option, and still the mistakes proliferate. Catching typos is easy (although not everyone does it). It’s the other stuff — correctly spelled but incorrectly wielded — that sneaks through and makes us look stupid. Here’s a quick review of some of the big ones.
#1: Loose for lose
#2: It’s for its (or god forbid, its’)
#3: They’re for their for there
#4: i.e. for e.g.
#5: Effect for affect
#6: You’re for your
#7: Different than for different from
#8 Lay for lie
#9: Then for than
#10: Could of, would of for could have, would have
(Source: ZDnet)