nav{
    position: fixed;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    max-width: 777px !important;
    height: auto;
    margin: 0 auto;
    border-top: 0.0238rem solid rgba(0,0,0,0.2);
    z-index: 99999;
    background: white;
}

nav *{
    box-sizing: border-box;
}
nav ul{
    display: block;
    width: 100%;
    height: 50px;
    background: white;
}
nav ul li{
    float: left;
    width: 20%;
    height: 100%;
}
nav ul li a{
    position: relative;
    display: block;
    width: 100%;
    height: 50px;
}
nav ul li a img{
    position: absolute;
    left: 50%;
    top: 50%;
    -webkit-transform: translate(-50%,-50%);
    transform: translate(-50%,-50%);
    height: 84%;

}