OK or okay; not ok. Fair enough, but I distinctly remember the word being rendered as okey back in the day. Was it an error or just a short-lived fashion? Apparently a nokay existed as a word for a short time, too.
Everyday or every day. That depends. You do this every day. The everyday problems continue.
To, too or two? Again, it depends. To is a proposition. He went to school. Too is an adjective (he was too tired) but it also exists as a synonym for as well. (He went too.) Two, obviously, is a number. There is a fourth homonym that formed the central mystery of one of the Black Widowers stories...
Alright or all right? Technically, all right is correct in every case.
Already or all ready? That depends. He was already there. She was all ready for the dance.
So there you have five common writing glitches I encounter over and over and over again. The five easy errors.