Tables

HTML

<table>
    <caption>Planetary Data</caption>
    <colgroup>
        <col>
    <colgroup class=data>
        <col>
        <col>
    <colgroup class=data>
        <col>
        <col>
    <thead>
        <tr>
            <th scope=col rowspan=2>Planet
            <th scope=colgroup colspan=2>Mass
            <th scope=colgroup colspan=2>Volume
        <tr>
            <th scope=col>kg
            <th scope=col>Earths
            <th scope=col>km<sup>3</sup>
            <th scope=col>Earths
    <tfoot>
        <tr>
            <th scope=row>Totals
            <td>
            <td>
            <td>
            <td>
    <tbody>
        <tr>
            <th scope=row>Mercury
            <td>3.3022e23
            <td>0.055
            <td>6.08300e10
            <td>0.056
        <tr>
            <th scope=row>Venus
            <td>4.8685e24
            <td>0.815
            <td>9.38000e11
            <td>0.857
        <tr>
            <th scope=row>Earth
            <td>5.9736e24
            <td>1
            <td>1.08321e12
            <td>1
    <tbody>
</table>

CSS

table {
    border:1px solid lime;
    border-collapse:collapse;
}
caption {
    border:1px solid black;
    margin-right:-2px;
    margin-left:-1px;
}
tbody {
    border:5px solid black;
}
caption, tr:nth-child(odd), col:nth-child(odd) {
    background:rgba(0,0,0,.1);
}
tbody td {
    text-align:right;
}
td, th {
    border:1px solid black;
}
colgroup {
    border:3px solid black;
}
colgroup.data col {
    width:5.5em;
}