ecco il mio codice, e' ok ma vorrei che la popup si aprisse a centro schermo...chi mi aiuta??

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<form action="http://www.html.it" method="get" style="margin-top:0px ; margin-bottom:0px" name="dettagli" onClick=target="foo" onsubmit="window.open('', 'foo', 'width=650,height=450,status=no,resizable=yes,scro llbars=yes')">
<div align="left">
<div align="left">
<table border="0" cellspacing="0" cellpadding="2" width="100">
<tr>
<td align="center" width="50"><font size="1" color="#777777" face="Verdana,Arial,Helvetica,Geneva,Swiss,SunSans-Regular">scheda</font></td>
<td>
<div align="left">
<input type="image" value="Submit" src="lens.gif" align="middle" border="0" alt="dettagli"></div>
</td>
</tr>
</table>
</div>
</form>
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Grazie in anticipo ..