@charset "UTF-8";

div.main_article {
    float: left;
    width: 75%;
}
div.archive_menu {
    float: right;
    width: 20%;
}

@media screen and (max-width: 540px) {
    div.main_article {
        float: none;
        width: 100%;
    }
    div.archive_menu {
        float: none;
        width: 100%;
    }

}