I often type "form" instead of "from," and spellcheckers don't ever catch that. When I type very quickly, I often meld words together when the start and end with similar letters. For example, if I were typing "Start the race" really fast I might type "Starthe race." Sometimes, when I am typing a string of very short word, like "is it in the," I will just skip one of the words. And I rather often type "hold on a sex" instead of "hold on a sec" when I'm chatting.