My list of words falling into this category of misuse by typo is lengthy, but I have a few favorites to share.
It seems common for sportswriters to use reign instead of the correct rein. "Summitt turned the coaching reigns over to Warlick."
Peak instead of peek. Judgement instead of judgment (just one "e"). Supercede instead of supersede. (No "c." Honest.)
Confusion about affect/effect. This troubled me for years until I learned the simple rule: Affect is a verb, effect is a noun; the exception is that effect becomes a verb only when vigorous action is applied.
Lots of smart people struggle with it's and its. First, you should amputate its' painlessly from your usage practice; it's an impossible construct. Next, use it's when you want to say it is. Use its to indicate possession. "It's a pain to remember the grammar rule and its proper application."
Enough for today. Permit a reminiscence. I once assisted an academic friend with a humungous treatise about the relationship, if any, between pornography and rape. Throughout, he had used
casual when
causal was called for. He remains grateful for my little bail-out job.