html {
    background-color: gray;
}
.centered {
    padding: 2%;
    width: 50%;
    margin: auto;
    background-color: white;
}

table {
    border-collapse: collapse;
    width: 100%;
    margin: auto;
}

th, td {
    border: 1px solid lightgray;
    text-align: left;
    padding: 10px;
}