No need to apologize for typos. If there were, I'd be permanently on my knees :-[
BTW some folks like using the spellchecker that's available when you're done typing a message, before clicking the Post button. Alternatively, you can always use the Modify button to fix a typo you notice later.
Speaking from my position as the Typo king, When I'm reading a message my mind usually just auto-corrects for typos of that type and puts in the missing/correct letter all by itself without my telling it to do so.