.m_lb_bg {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    overflow: hidden;
    z-index: -1;
}

.m_lb_bg .a {
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    z-index: 1;
}

.m_lb_bg .a .img {
    position: absolute;
    left: 50%;
    top: 0;
    width: auto;
    height: 100%;
    margin-left: -960px;
}