Sustituye tu codigo por este:
Forest brat<br />
<br />
<table cellspacing="0" cellpadding="0" _mce_style="margin: 0 0 10px 0; width: 244px; background: #fff; border: 1px solid #F3F3F3;" style="margin: 0pt 0pt 10px; width: 244px; background: none repeat scroll 0% 0% rgb(255, 255, 255); border: 1px solid rgb(243, 243, 243);">
<tbody>
<tr>
<td _mce_style="font-family: verdana; font-size: 11px; color: #000; padding: 5px 5px;" style="font-family: verdana; font-size: 11px; color: rgb(0, 0, 0); padding: 5px;"><div id="juegoFlash" style="width:640px; height:480px;">
<object style="z-index:1"height="100%" width="100%" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000">
<param value="http://www.games68.com/games/game-1246062349.swf" name="movie" />
<param value="high" name="quality" />
<param value="false" name="menu" />
<embed height="100%" width="100%" menu="false" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" quality="high" _mce_src="http://www.games68.com/games/game-1246062349.swf" src="http://www.games68.com/games/game-1246062349.swf" wmode="transparent"></embed> <center> </center></object>
</div></td>
</tr>
<tr>
<td align="center" _mce_style="font-family: verdana; font-size: 11px; padding: 5px 10px; border-top: 1px solid #F3F3F3;" style="font-family: verdana; font-size: 11px; padding: 5px 10px; border-top: 1px solid rgb(243, 243, 243);"> </td>
</tr>
</tbody>
</table>
<input type="button" value="Aumentar" onclick="tamañoGrande()">
<input id="botonTamañoNormal" type="button" value="Tamaño normal" style="z-index:2;display:none;position:absolute;bottom:0;ri ght:0;" onclick="tamañoNormal()">
<script type="text/javascript">
function tamañoGrande(){
document.getElementById('juegoFlash').style.positi on = 'absolute';
document.getElementById('juegoFlash').style.top = '0';
document.getElementById('juegoFlash').style.left = '0';
document.getElementById('juegoFlash').style.height = '100%';
document.getElementById('juegoFlash').style.width = '100%';
document.getElementById('botonTamañoNormal').style .display = 'block';
}
function tamañoNormal(){
document.getElementById('juegoFlash').style.positi on = 'relative';
document.getElementById('juegoFlash').style.top = '0';
document.getElementById('juegoFlash').style.left = '0';
document.getElementById('juegoFlash').style.height = '640px';
document.getElementById('juegoFlash').style.width = '480px';
document.getElementById('botonTamañoNormal').style .display = 'none';
}
</script>