div.layout-master-detail {
    margin-bottom: 15px;
    }
    div.layout-master-detail:after { content: "."; display: block; height: 0; clear: both; visibility: hidden; }
    
    @media screen and (max-width: 1240px) {
        div.layout-master-detail > div.column-left {
            margin-bottom: 15px;
            }
        div.layout-master-detail > div.column-right {
            margin-bottom: 15px;
            }
    }
    @media screen and (min-width: 1240px) {
        div.layout-master-detail > div.column-left {
            float: left;
            margin-right: 20px;
            width: 320px;
            }
        div.layout-master-detail > div.column-right {
            float: left;
            width: 860px;
            }
    }