header {
   background-color: yellow;
   text-align: center;
}
nav {
    background-color: orange;
    float:left;
    line-height:30px;
    text-align: center;
    height: 600px;
    width:  10%;
    padding: 5px;
}
aside {
    background-color: lightgreen;
    float:right;
    line-height:30px;
    text-align: center;
    height: 600px;
    width:  10%;
    padding: 5px;
}
section {
    background-color: yellowgreen;
    margin: 0 auto;
    width: 75%;
    padding:10px;
}

footer {
    height: 70px;
    padding: 5px;
    clear: both;
    text-align:center;
    background-color:black;
    color:white;
}