tr > td:nth-child(1) {
    font-weight: bold;
}
* {
    font-family: sans-serif;
}
main {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    width: 900px;
    max-width: calc(100% - 10px);
    padding: 5px;
}
td {
    padding: 10px 0;
}

body, html {
    padding: 0;
    margin: 0;
}

header {
    background: #3399ff;
    padding: 10px;
    width: 100%;
    text-align: center;
}

header a {
    text-decoration: none;
    color: #000;
    padding: 10px;
    font-weight: bold;
}
header a:hover {
    background: #99ccff;
}

h1 {
    text-align: center;
}