html {
    display: table;
    margin: auto;
}
html, body {
    height: 100%;
}
body {
    background-color: #ffffd0;
    display: table-cell;
    vertical-align: middle;
    text-align: center;
}
a {
    border: 3px green ridge;
    text-decoration: none;
}
h1, h2, h3 {
    color: #d00000;
}
a:hover {
    color: white;
    background-color: green;
}
div {
    border: 1px solid green;
    margin: 20px;
    min-height: 60px;
}