header {
    position: absolute;
    top: 0px;
    left: 0px;
    width: 100px;
    height: 50px;
}

menu {
    position: absolute;
    top: 0px;
    left: 0px;
    width: 100px;
    height: 100px;
}

#menu a {
    background-color: white;
    padding: 10px;
}

#menu a:hover {
    background-color: black;
    color: white;  
    padding: 10px;
}