Question

Is that possible not to indent cells in th?
http://jsfiddle.net/kWTte/1/

HTML

<table>
    <th>
        <td></td>
        <td></td>
    </th>
    <tr>
        <td></td>
        <td></td>
    </tr>   
</table>

Answer 1

You can think of th as the equivalent of td, but for table’s header.
So ths should be contained into a tr element.

The correct form is:

<table>
    <tr>
        <th>Header one</th>
        <th>Header two</th>
    </tr>
    <tr>
        <td>1</td>
        <td>2</td>
    </tr>   
</table>

If you need to wrap the table header you could use thead.
Similarly you could use tbody for the body of the table (note that you can have more than one tbody in the same table).