Also: "payed" vs. "paid"; in grammar, "well" vs "good".
"your" and "You're" is my pet hate
Let's not forget about "it's" and "its".
Apostrophe mistake's are pretty jarring; seeing one is like tripping over a rock, for me.
I can let any spelling mistake or grammatical murder slide except this one. I won't comment on it as that's a bit petulant, but I will seethe inside and often, almost without thinking, I'll disregard whatever else they wrote.