.nav_l_b ul li span {
        position: absolute;
    top: -10px;
    right: 10px;
    width: 1rem;
    cursor: pointer;
    height: 1rem;
    display: block;
    margin-top: 2.5rem;
    font-size: 1.2rem;
    float: right;
    color: #B3B3B3;
    background-image:url(images/jiahao.png);
    background-repeat: no-repeat;
    background-position: center;}
.open {
    background-image:url(images/jianhao.png)!important;}
.a_bgg:hover{ color:#016BFF;}