ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    display: inline-block;
}

.div_center {
    text-align: center;
}

li {
    float: left;
}

    li a {
        display: block;
        text-align: center;
        padding: 14px 16px;
        text-decoration: none;
    }