Ever heard the expression to error is human...to really screw things up you need a computer? Well...now think what happens when you combine the two!
Ok...so here is a question for you...have you ever made an error before when using the computer? A simple mistyping of a word...you meant to say the word goal and instead you type coal. You perform spell check and all seems good. You discover only after you have sent your work of art to someone that there are typos!