.aside{
    position: absolute;
    top: 500px;
    left: 50%;
    /* margin-left: 版心宽度 + 20 px */
    margin-left: 420px;
    width: 70px;
    background-color: #eee;
    outline: 1px solid #ccc;
}
.aside ul li:nth-child(odd){
    height: 50px;
    width: 70px;
    text-align: center;
    line-height: 50px;
}
.aside ul li:nth-child(even){
    height: 1px;
    width: 50px;
    background-color: #ccc;
    margin: 0 auto;
}
.aside ul li a{
    display: block;
    height: 100%;
    width: 100%;
}
.aside .gotop{
    display: none;
}