In http://nesdev.com/6502.txt , there are at least two errors in the section that goes over the ADC instruction and its opcodes.
It lists the opcodes for instructions of the form "ADC $ABCD" and "ADC $ABCD, X" as 0x60 and 0x70 respectively, but this is contradicted by two other documents ( http://nesdev.com/opcodes.txt ) and 6502jsm.doc in ( http://nesdev.com/6502jsm.zip ), which state that the opcodes are 0x6d and 0x7d respectively.
Sorry if this was already mentioned. I ran a couple of searches but they didn't turn up anything that looked related on this message board.
It lists the opcodes for instructions of the form "ADC $ABCD" and "ADC $ABCD, X" as 0x60 and 0x70 respectively, but this is contradicted by two other documents ( http://nesdev.com/opcodes.txt ) and 6502jsm.doc in ( http://nesdev.com/6502jsm.zip ), which state that the opcodes are 0x6d and 0x7d respectively.
Sorry if this was already mentioned. I ran a couple of searches but they didn't turn up anything that looked related on this message board.