body {
    font-family: Helvetica, sans-serif;
    background-color: lightgray;
    margin: 0;
    
}

header div {
    text-align: center;
}

header nav {
    background-color: black;
    color: white;
    padding: 0;
    width: 100%;
    box-sizing: border-box;
}

header nav ul {
    list-style: none;
    margin: 0;
    padding: 15px;
    text-align: center;
}

header nav li {
    display: inline;
    padding: 10px;
}

header nav a:link,
header nav a:visited {
    color: white;
    text-decoration: underline;
}


main{
    background-color: white;
    box-sizing: border-box;
    width: 70%;
    margin: 15px auto;
    border: 3px solid grey;
    padding: 15px;
    
}

footer{
   text-align: center;
}