  We calculate frequency and temperature dependence of the anomalous ac Hall
conductivity induced by impurity scattering in a chiral px+ipy superconductor,
such as Sr2RuO4, with spontaneous time-reversal-symmetry breaking in the
absence of an external magnetic field. We consider two models of disorder,
Gaussian and non-Gaussian, characterized by the second and third moments of the
random impurity potential, respectively. Within both models, we find that the
anomalous Hall conductivity has a finite real value at zero frequency, exhibits
singularities at the threshold of photon absorption across the superconducting
gap, and decays as some power of the high frequency \Omega. The Hall
conductivity increases linearly with the decrease of temperature below the
superconducting transition and saturates at zero temperature. Using our results
for the high-frequency Hall conductivity, we estimate the polar Kerr angle for
light reflection from the material and compare it with the experimental
measurements in Sr2RuO4 by Xia et al., Phys. Rev. Lett. 97, 167002 (2006).
