body {
    font-family: Arial;
}
ul {
    margin: 0px;
    padding: 0px;
    list-style: none;
}
ul li {
    float: left;
    width: 200px;
    height: 40px;
    background-color: #1E460F;;
    line-height: 40px;
    text-align: center;
    font-size: 20px;
}
ul li a {
    text-decoration: none;
    color: white;
    display: block;
}
ul li a:hover {
    background-color: green;
}
ul li ul li {
    display: none;
}
ul li:hover ul li {
    display: block;
}