Byte contains the 8 Bits and bit contains either the value 
0 or 1. there are only two states there will be 255 
combinations i.e.(2 raise to power 8 minus 1) 
combinations  .

There'll actually be 256 combinations. The maximum value
that can be represented with a byte (8 - bits) is 255 but as
far as combinations are concerned 0 should also be
considered as well as 1, 2, 3, ..., 255. So there are total
256 combinations.

ya they r right.

2 raise to no. of byte ie. for three byte ,8 bit combination

the first two answers are right

256 combinations.Byte contains the 8 Bits and bit contains 
either the value 0 or 1.i.e.(2 raise to power 8 minus 
1).The maximum number of value represented with a byte is 8 
bits is 255 but 0 should also be considered as well as 1, 
2, 3, ..., 255. So there are total
256 combinations.

it is 2^8
means 2 ^ no of bits
means 256....
:)