#d {
    display:block;
    max-width: 600px;
    max-height: 424px;
    border: 1px solid #eeeeee;
}

#m {
    display:none;
    max-width: 310px;
    max-height: 220px;
}


@media only screen and (max-width:500px) {
    #d {
        display:none;
    }

    #m {
        display:block;
        max-width: 310px;
        max-height: 220px;
    }
}