Which spelling mistakes make your blood boil?

I hate it even more so when it's deliberate, for example when people use text speak. I've seen it right here on mylot, people using words such as dis, dat, a da uver. It makes me cringe & makes them look like imbeciles

some spellings that get next to me are: Their, instead of there Using has and have incorrectly, the contractions are always misused. There are more, can't think of them all right now.

All spelling errors make my blood boil, but some more than others. For instance, the word okay. In most spell checking programs, this word is not spelled correctly. HUH? When did that happen? I realize that I went to school years ago but that was the correct spelling then. Oddly enough, on one spell checkers I used okay is not spelled right and neither is ok LOL By the way, after cleaning chalkboards for 25 years I can tell you the worst spellers in the world are teachers LOL