Local electromagnetic field fluctuations and related enhancement of nonlinear phenomena in metal-dielectric composites near the percolation threshold (percolation composites) have recently become an area of active study, because of the many fundamental problems involved and the high potential for various applications. It has been recognized recently that local field fluctuations can be especially large in the optical and infrared spectral ranges due to the surface plasmon resonance in metallic granules and their clusters. The strong fluctuations of the local electric and magnetic fields...