What's the best way to represent an empty TH in HTML5? - html

Question

Say I have the given table:
+------+------+------+
| Col1 | Col2 | Col3 |
+------+------+------+------+
| Row1 | D1.1 | D1.2 | D1.3 |
+------+------+------+------+
| Row2 | D2.1 | D2.2 | D2.3 |
+------+------+------+------+
| Row3 | D3.1 | D3.2 | D3.3 |
+------+------+------+------+
And I want to represent it in HTML5. The tricky thing is that tables like this must be semantically important, but the top-left cell is not semantically important, but instead a spacer to line up the more important column headers. What's the best way to do this? My first idea is to do it like this:
<table>
<thead>
<tr>
<th></th>
<th>Col1</th>
<th>Col2</th>
<th>Col3</th>
</tr>
</thead>
<tbody>
<tr>
<th>Row1</th>
<td>D1.1</td>
<td>D1.2</td>
<td>D1.3</td>
</tr>
<tr>
<th>Row2</th>
<td>D2.1</td>
<td>D2.2</td>
<td>D2.3</td>
</tr>
<tr>
<th>Row3</th>
<td>D3.1</td>
<td>D3.2</td>
<td>D3.3</td>
</tr>
</tbody>
</table>
Though, putting <th></th> in there feels just wrong, like using <p> </p> for spacing. Is there a better way to do this?

Answer 1

It's completely acceptable to have an empty <th> element, speaking in terms of either validity or semantics. Nothing in the spec forbids it; in fact, it contains at least one example that makes use of an empty <th> for this very purpose:
The following shows how one might mark up the gross margin table on page 46 of Apple, Inc's 10-K filing for fiscal year 2008:
<table>
<thead>
<tr>
<th>
<th>2008
<th>2007
<th>2006
<tbody>
<tr>
<th>Net sales
<td>$ 32,479
<td>$ 24,006
<td>$ 19,315
<!-- snip -->
</table>

Answer 2

For a discussion about semantics and empty table elements I would like to refer to this question on StackOverflow
Styling of "empty" cells (like background or borders) can sometimes depend on the absence/presence of "content" that is why people often put a inside. There is a special CSS tag for styling empty cells you can read about it here on MDN.
table {
empty-cells: hide;
}
Here you can find another article with some nice background information on this topic.

Answer 3

Any better way of using empty <th></th>:
Exact code:
<tr>
<th></th>
<th colspan="6"></th>
</tr>