“…then the cCntentS of column D will move left to column E. errors do not occur [41, p. 3241. The facts go another way: error detection, diagnosis, and recovery consume somewhere between a quarter and half of the user's time ([19], [22], [23], [37], [45], and studies of Davis and Magers mentioned in [17]). Any realistic approach to instruction and documentation must focus substantial attention on errors.…”