Prueba así
<html>
<head>
<% if Request.Querystring("resolucion")="" then%>
<script>
var ancho,alto, url
if ((screen.width == 800) && (screen.height == 600)){
ancho="800"
alto="600";
url="default.asp?resolucion=1"}
else if ((screen.width == 1024) && (screen.height == 768)){
ancho="1024"
alto="768";
url="default.asp?resolucion=2"}
else if ((screen.width == 1152) && (screen.height == 864)){
ancho="1152"
alto="864";
url="default.asp?resolucion=3"}
else if ((screen.width == 1280) && (screen.height == 1024)){
ancho="1280"
alto="1024";
url="default.asp?resolucion=4"}
else{
window.location.href = "default.asp?resolucion=5"}
function Entrar(){
window.location.href=url}
window.onload = Entrar()
</script>
<%else%>
<%
Dim resolucion
resolucion=Request.Querystring ("resolucion")
end if
%>
</head>
<body bgcolor="#FFE502" scroll="no" >
<%if resolucion=1 then%>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td><div align="center">
<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="800" height="600">
<param name="movie" value="Pelicula2.swf">
<param name="quality" value="high">
<embed src="Pelicula2.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="800" height="600"></embed>
</object>
</div>
</div></td>
</tr>
</table>
<%elseif resolucion=2 then%>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td><div align="center">
<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="1024" height="768">
<param name="movie" value="Pelicula2.swf">
<param name="quality" value="high">
<embed src="Pelicula2.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="1024" height="768"></embed>
</object>
</div>
</div></td>
</tr>
</table>
<%elseif resolucion=3 then%>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td><div align="center">
<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="1152" height="864">
<param name="movie" value="Pelicula2.swf">
<param name="quality" value="high">
<embed src="Pelicula2.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="1152" height="864"></embed>
</object>
</div>
</div></td>
</tr>
</table>
<%elseif resolucion=4 then%>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td><div align="center">
<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="1280" height="1024">
<param name="movie" value="Pelicula2.swf">
<param name="quality" value="high">
<embed src="Pelicula2.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="1280" height="1024"></embed>
</object>
</div>
</div></td>
</tr>
</table>
<%elseif resolucion=5 then%>
Por Favor elige la resolución en que quieres ver la pagina:
<br>
<a href="default.asp?resolucion=1">800 x 600</a>
<br>
<a href="default.asp?resolucion=1">1024 x 768</a>
<br>
<a href="default.asp?resolucion=1">1152 x 864</a>
<br>
<a href="default.asp?resolucion=1">1280 x 1024 </a>
<%end if%>
</body>
</html>
a ver si así deja de darte el error....
