AVR-Chat

I am getting:
wirelessmouse.c:213: warning: comparison is always true due to limited
range of data type

for the line:
if ((byte_index >=0) && (byte_index < 8))

where byte_index is delared as:
unsigned char byte_index;


This was taken from someone elses "working" code, but I have just
spent the past 4 hours rewriting large sections because they simply
would not compile (it said that it was written for winavr, but I'm
thinking that it must have been for a different compiler due to all
the syntax errors.)  I have finally gotten it to compile but I have
several of these identical warnings remaining.

Someone please help me,
    Daniel