Not exactly sure what you are trying to do
But the file name would have to be a php file - myFile.php etc. Then you would have to echo the mark-up something like this.
<?php
echo '<table width="100%" cellpadding="0" cellspacing="0" border="0">
<tr>
<td class="bgextra">
<div align="center">
<a href="blah/index.php?">Some tag or image</a>
</div>
</td>
</tr>
</table>
';
?>
If you have other apostrophes in whatever you add then you would need to comment them out like so.
<?php
echo '<table width=\'100%\' cellpadding=\'0\' cellspacing=\'0\' border=\'0\'>
<tr>
<td class=\'bgextra\'>
<div align=\'center\'>
<a href=\'blah/index.php?\'>Some tag or image</a>
</div>
</td>
</tr>
</table>
';
?>
As I said - Not exactly sure what you are trying to do?