<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script language="JavaScript" type="text/JavaScript">
<!--
function MM_checkPlugin(plgIn, theURL, altURL, autoGo) { //v4.0
var ok=false; document.MM_returnValue = false;
with (navigator) if (appName.indexOf('Microsoft')==-1 || (plugins && plugins.length)) {
ok=(plugins && plugins[plgIn]);
} else if (appVersion.indexOf('3.1')==-1) { //not Netscape or Win3.1
if (plgIn.indexOf("Flash")!=-1 && window.MM_flash!=null) ok=window.MM_flash;
else if (plgIn.indexOf("Director")!=-1 && window.MM_dir!=null) ok=window.MM_dir;
else ok=autoGo; }
if (!ok) theURL=altURL; if (theURL) window.location=theURL;
}
//-->
</script>
</head>

<body onLoad="MM_checkPlugin('Shockwave Flash','','sito.it',false);return document.MM_returnValue">
</body>
<script name="Used by MM_checkPlugin" language="javascript">
<!--
with (navigator) if (appName.indexOf('Microsoft')!=-1 && appVersion.indexOf('Mac')==-1) document.write(''+
'<scr'+'ipt language="VBScript">\nOn error resume next\n'+
'MM_dir = IsObject(CreateObject("SWCtl.SWCtl.1"))\n'+
'MM_flash = NOT IsNull(CreateObject("ShockwaveFlash.ShockwaveFlash "))\n</scr'+'ipt>');
//-->
</script>
</html>

Questo codice rileva la presenza del plug-in flash e in assenza indirizza all'URL sito.it (cambialo con quello che preferisci.