Here is an example of a table being used to mark up a Sudoku puzzle. Observe the lack of headers, which are not necessary in such a table.
<style>
#sudoku { border-collapse: collapse; border: solid thick; }
#sudoku colgroup, table#sudoku tbody { border: solid medium; }
#sudoku td { border: solid thin; height: 1.4em; width: 1.4em; text-align: center; padding: 0; }
</style>
<h1>Today's Sudoku</h1>
<table id="sudoku">
<colgroup><col><col><col>
<colgroup><col><col><col>
<colgroup><col><col><col>
<tbody>
<tr> <td> 1 <td> <td> 3 <td> 6 <td> <td> 4 <td> 7 <td> <td> 9
<tr> <td> <td> 2 <td> <td> <td> 9 <td> <td> <td> 1 <td>
<tr> <td> 7 <td> <td> <td> <td> <td> <td> <td> <td> 6
<tbody>
<tr> <td> 2 <td> <td> 4 <td> <td> 3 <td> <td> 9 <td> <td> 8
<tr> <td> <td> <td> <td> <td> <td> <td> <td> <td>
<tr> <td> 5 <td> <td> <td> 9 <td> <td> 7 <td> <td> <td> 1
<tbody>
<tr> <td> 6 <td> <td> <td> <td> 5 <td> <td> <td> <td> 2
<tr> <td> <td> <td> <td> <td> 7 <td> <td> <td> <td>
<tr> <td> 9 <td> <td> <td> 8 <td> <td> 2 <td> <td> <td> 5
</table>
<style type="text/css">
#sudoku { border-collapse: collapse; border: solid thick; }
#sudoku colgroup, table#sudoku tbody { border: solid medium; }
#sudoku td { border: solid thin; height: 1.4em; width: 1.4em; text-align: center; padding: 0; }
</style>
1 | | 3 | 6 | | 4 | 7 | | 9
|
| 2 | | | 9 | | | 1 |
|
7 | | | | | | | | 6
|
2 | | 4 | | 3 | | 9 | | 8
|
| | | | | | | |
|
5 | | | 9 | | 7 | | | 1
|
6 | | | | 5 | | | | 2
|
| | | | 7 | | | |
|
9 | | | 8 | | 2 | | | 5
|