Centering

my flash website is 640x480, how would i center the movie in the web browser?

<table width="100%" height="100%" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td>
	  <embed src="mymovie.swf" height="480" width="640"></embed>
	</td>
  </tr>
</table>