Making an ugly iframe, pretty and mobile friendly

Site URL: https://www.fresnohumane.org/adoptable-dogs

I need to learn how to make an iframe more appealing and mobile friendly.    

Add this to Home >D esign > Custom CSS

@media screen and (max-width:640px) {
div#block-yui_3_17_2_8_1473122406196_5795 iframe {
    width: 100%;
}
}