The given equation is:
\[
4^{8x} = 256
\]
Now, we can express both sides of the equation with base 4:
\[
256 = 4^4
\]
So the equation becomes:
\[
4^{8x} = 4^4
\]
Since the bases are the same, we can equate the exponents:
\[
8x = 4
\]
Now, solving for \(x\):
\[
x = \frac{4}{8} = \frac{1}{2}
\]
Thus, the value of \(x\) is \(\frac{1}{2}\), so the correct answer is (C).