.b_body{
    min-height:100%;
    position: relative;
}
.b_body_c{
    padding-bottom: 240px;
    min-height: 100%;
}
.b_body_f{
    bottom:0;
    min-height: 240px;
    position:absolute;
    width:100%;
}
/* HTML
<div class="b_body">
    <div>
        <div class="b_body_c">
            <div class="b_head">
                    <!-- header -->
                <div class="br"></div>
            </div>
            <div class="b_body_f">
                    <!-- footer -->
            </div>
        </div>
    </div>
</div>
*/