C-symmetry means the symmetry of physical laws over a charge-inversion transformation. This is not believed by physicists to be the case for the actual universe.
The laws of electromagnetism, both classical and quantum are invariant under this transformation: if each charge q were to be replaced with an equivalent opposite charge -q in all of the equations of electromagnetism, the laws would preserve the same form. However, this symmetry appears to be violated in observation, owing to the fact that (at least the nearby part of) our physical universe is made up of matter and not anti-matter. Though, in principle, the choice of 'positiveness' or 'negativeness' is only a convention, in reality, asymmetry of charge is an observed fact. Thus, the violation of C-symmetry is considered a fundamental physical property of the universe.
It was believed for some time that this could be combined with the parity-inversion transformation (see P-symmetry) to preserve a so-called CP-symmetry. However, violations of even this symmetry have now been identified. As of 2004, physicists believe that a stronger CPT-symmetry that also factors in time-reversal is, indeed, preserved.