/* 基本設定 */
html,body{
    height: 100%;
}
body {
    background-color: white;
    margin: 0;
    padding: 0;
    border: 0;
}
a {
    text-decoration: none;
    color: chocolate;
}
a:hover {
    color: brown;
}

/* 中央寄せ */
div.center {
    height: 100%;
    position: relative;
}
div.center p {
    font-family: monospace;
    font-size: large;
    margin: 20px 0;
    padding: 20px;
    background: lightblue;
    position: absolute;
    top: 40%;
    left: 50%;
    margin-right: -50%;
    transform: translate(-50%, -50%);
}