h1 {
    text-align: center;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
}

ul {
    display: flex;
    justify-content: center;
    list-style-type: none;
}

ul li{
    flex: 0 1 auto;
    width: 200px;
    height: 40px;
}

a {
    background-color: yellow;
}