Hola,
Aquí te pomgo el HTML de cómo lo hago yo:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<style type="text/css">
<!--
HTML { overflow:auto; height:100% }
A {text-decoration:none;font-size:10px; }
BODY{
background-color:#F4F3F0;
margin: 0px;
padding: 0px;
border: 0px;
width: 100%;
height:100%;
font-size: 10px;
font-family: Verdana, Arial, Helvetica, sans-serif;
}
-->
</style>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>TU TÍTULO</title>
</head>
<body>
<table width="100%" height="100%">
<tr>
<td align="center" valign="middle" style="font-size:0px;">
<!-- AQUI VA TU FLASH -->
<object>
<embed></embed>
</object>
</td>
</tr>
</table>
</body>
</html>