@media (max-width:679px) {
    .banner-fixo a img.banner-desktop {
        display: none;
        visibility: hidden;
    }
    .banner-fixo a img.banner-mobile {
        display: block;
        visibility: visible;
    }
}
@media (min-width:680px) {
    .banner-fixo a img.banner-desktop {
        display: block;
        visibility: visible;
    }
    .banner-fixo a img.banner-mobile {
        display: none;
        visibility: hidden;
    }
}