The optical and magneto-optical properties of amorphous CoFeSiB ribbons were investigated for incident photons in the energy range from 0.05 to 2.2 eV. The Kerr rotation spectra for the amorphous films have a shape in the 0.6 - 2.2 eV region that is quite similar to that of bulk Co. The optical conductivity of the amorphous CoFe(Ni)SiB alloys increases slowly as a function of frequency (proportional to omega (1/3)) in the IR. Such a sigma-omega (1/3) dependence in the IR suggests an additional localization of the electron states. A large room-temperature magnetoresistance effect has been demonstrated in thin Co71Fe7Si12B10 and Co59Fe5Ni10Si11B15 amorphous ribbons for alternating current at applied fields, H < 80 Oe.