body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    height: 100%;
    width: 100%;
    display: table;
}

.topnav {
    overflow: hidden;
    background-color: #333;
}

    .topnav a {
        float: left;
        color: #f2f2f2;
        text-align: center;
        padding: 14px 16px;
        text-decoration: none;
        font-size: 17px;
    }

        .topnav a:hover {
            background-color: #ddd;
            color: black;
        }

        .topnav a.active {
            background-color: #4CAF50;
            color: white;
        }

footer {
    text-align: center;
    background-color: grey;
    display: table-row;
    height: 0;
}

.blue {
    color: deepskyblue;
}

.link {
    color: #337ab7;
    text-decoration: none;
}