@media (max-width: 640px) {
    #talk_body .txt_box .desc p {
        margin: 0 0 5px 0;
        line-height: 1.8em;
        font-size: .85rem;
    }
}

@media (min-width: 641px) {
    #talk_body .txt_box .desc p {
        margin: 0 0 5px 0;
        line-height: 1.8em;
    }
}

element.style {
    margin: 20px;
}