Centered pop up issue

Hey guys, thanks heaps for your help earlier with the border thing, appreciated.

Now im trying to get a centered pop up to work, heres my script currently;

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Shudder Productions</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>

<body>
<style type="text/css">
<!--
body {
margin-left: 0px;
margin-top: 0px;
margin-right: 0px;
margin-bottom: 0px;
}
-->
</style>
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0" width="768" height="576">
  <param name="movie" value="http://shudderproductions.com/tmp/ShudderProductions.swf">
  <param name="quality" value="high">
  <embed src="http://shudderproductions.com/tmp/ShudderProductions.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="768" height="576"></embed></object>

</body>
</html>

Ive been looking around on tutorials for this but im a little confused, can anyone point me in the right direction?

Cheers :mario: