Filter Drop Shadow

.filter-drop-shadow {
    -webkit-filter: drop-shadow(0 1px 2px rgba(0,0,0,.5));
    -moz-filter: drop-shadow(0 1px 2px rgba(0,0,0,.5));
    -ms-filter: drop-shadow(0 1px 2px rgba(0,0,0,.5));
    -o-filter: drop-shadow(0 1px 2px rgba(0,0,0,.5));
    filter: drop-shadow(0 1px 2px rgba(0,0,0,.5));
}

Antes de implementarlo verifica la compatibilidad entre navegadores.