body {
    width: 100%;
    *zoom: 1;
}

body:before,
body:after {
    content: "";
    display: table;
}

body:after {
    clear: both;
}

#maincolumn {
    display: inline;
    float: left;
    width: 80%;
}

#sidebar {
    display: inline;
    float: left;
    width: 20%;
}

@media screen and (max-width: 720px) {
    #maincolumn,
    #sidebar {
        float: left;
        width: 100%;
    }

    #maincolumn {
        display: inline;
    }

    #sidebar {
        display: none;
    }
}