table.prefix {
    border: 4px solid black;
    border-spacing: 0em;
    border-collapse: collapse;
}

table.prefix td {
    border: 2px solid black;
    text-align: center;
    padding: .25em .25em;
    font-size: 120%;
    font-family: sans-serif;
}

table.prefix td.na {
    background-color: gray;
    color: gray;
}

table.prefix h2 {
    margin: .25em;
}