时间轴制作（响应式）Common.css

#pawtop {
    background: url(../../images/icon/pawtop.png) no-repeat;
    cursor: default;
    display: block;
    height: 250px;
    margin: -125px 0 0;
    position: fixed;
    right: 0;
    top: 80%;
    z-index: 11;
}

    #pawtop, #pawtop div {
        overflow: hidden;
        padding: 0;
        width: 149px;
    }

        #pawtop div {
            left: 0;
            margin: 0;
            position: absolute;
            top: 0;
        }

        #pawtop .top-1 {
            background: url(../../images/icon/pawtop.png) -149px 0 no-repeat;
            display: block;
            height: 250px;
            opacity: 0;
            z-index: 2;
        }

        #pawtop .top-2 {
            background: 0 0;
            cursor: pointer;
            display: block;
            height: 150px;
            z-index: 3;
        }

@media only screen and (max-width: 768px) {
    /*屏幕太小就隐藏返回顶部*/
    #pawtop {
        display: none !important;
    }
}