I was reading about avr usart communications and how to implement it, when I found a formula which determines the baud rate:
BaudValue = ((F_CPU / (USART_BAUDRATE * 16)) - 1
F_CPU = main clock frequency
USART_BAUDRATE = desired baud rate
BaudValue = a value needs to be written to some registers which implement it into the usart subsystem
According to the table in http://www.wormfood.net/avrbaudcalc.php
none of the 16MHz entry is 100% error-free
So, how does arduino handle communication so good?