xs1n0g01 - signature byte 1 MSBit reset to zero
xs2n0g01 - signature byte 2 is a 'Q'
xs4n0g01 - signature byte 4 lowercase
xs7n0g01 - 7th byte a space instead of control-Z
xcrn0g04 - added cr bytes
xlfn0g04 - added lf bytes
xhdn0g08 - incorrect IHDR checksum
xc1n0g08 - color type 1
xc9n2c08 - color type 9
xd0n2c08 - bit-depth 0
xd3n2c08 - bit-depth 3
xd9n2c08 - bit-depth 99
xdtn0g01 - missing IDAT chunk
xcsn0g01 - incorrect IDAT checksum 