Header information in a table are defined with the <th> tag.
All major browsers will display the text in the <th> tag as bold and combined.
An example for tables :
<table border="1">
<tr>
<th> header1 </th>
<th> header2 </th>
</tr>
<tr>
<td> row1,cell1</td>
<td> row1,cell2</td>
</tr>
<tr>
<td> row2,cell1 </td>
<td> row2,cell2 </td>
</tr>
</table>
