"No spaces or characters", I'll have to remember that next time I make a form that shouldn't be used. I used to have a fifteen-digit number on a visa or master

"No spaces or characters", I'll have to remember that next time I make a form that shouldn't be used. I used to have a fifteen-digit number on a visa or mastercard (not amex), which was a little weird, but I was amazed how many vendors couldn't handle it. Aren't there standards for this stuff?