header { background-color: red;
height: 100px;
width: 100%;
margin: 0px;
text-align: center;
line-height: 100px;
color: antiquewhite;
border-bottom: 2px solid black;
}
nav ul li {
    float: left;
    list-style: none;
    margin: 20px;
    line-height: 10px;
}