<tr> inside <td> not displayed properly - html

Question

Can anybody tell me why my internal rows are not coming inside the td.
<tr id="group_1_id">
<th>Group 1</th>
<td>
<tr id="1"><td>1</td><td>One</td><td><input type="text" name="one" value="one"/></td></tr>
<tr id="2"><td>2</td><td>Two</td><td><input type="text" name="two" value="two"/></td></tr>
<tr id="3"><td>3</td><td>Three</td><td><input type="text" name="three" value="three"/></td></tr>
</td>
</tr>
The 3 table rows comes outside the parent tr. Though they are defined inside the td of my parent tr.
Thanks in advance

Answer 1

I would say that your HTML is not correct. If you want a header section, then use <thead> or <tbody> element, not <th>. I believe your problems emerged from the fact that you have used <th> instead of <thead>.
You may want to use a validator to check whether your HTML is correct. Upload your page to http://validator.w3.org for example, and correct the errors it shows you.
Also check the specification (for example on www.whatwg.org) because I suppose that you wanted to create more than one header section in a table. A table may have not more than one <thead>, not more than one <tfoot>, and any number of <tbody> elements.
Oh, you have just reedited the question, but the problem is the same :)
A <tr> element cannot be placed inside a <td> or <th>. When that code is parsed, a nested table is automagically created, so the real HTML looks like this:
<tr id="group_1_id">
<th>Group 1</th>
<td>
<table>
<tbody>
<tr id="1"><td>1</td><td>One</td><td><input type="text" name="one" value="one"/></td></tr>
<tr id="2"><td>2</td><td>Two</td><td><input type="text" name="two" value="two"/></td></tr>
<tr id="3"><td>3</td><td>Three</td><td><input type="text" name="three" value="three"/></td></tr>
</tbody>
</table>
</td>
</tr>