Surface excitation in r.f.-sputtered thin amorphous (Gd1?xCox)1?yMoy films was studied. A microwave spectrometer operating in the X band was used for magnetic resonance investigations; the external magnetic field was rotated from perpendicular to parallel resonance orientation. The critical angle and angular dependence of the position of the surface mode and the uniform mode were determined. The surface inhomogeneity (SI) model was applied with symmetrical boundary conditions. The surface anisotropy energy term was assumed to be a superposition of the uniaxial anisotropy term and a biaxial anisotropy term. The origin of the latter term has not yet been established. We also performed resonance experiments at various temperatures ranging from 180 to 300 K. The temperature dependences of the uniaxial surface anisotropy constant Ks1? and the biaxial surface anisotropy constant Ks2? were found from the results of these experiments. The uniaxial anisotropy energy varies with temperature and changes sign from easy axis to easy plane at y = 0.02, whereas the biaxial surface anisotropy does not change character.