Grazie per aver risposto.
Questo script funziona... ma non so se è corretto...

codice:
<html>
<head>
<script 
src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js" 
type="text/javascript"></script>
<script type="text/javascript">
       $(document).ready(function(){
               $('#contentArea').load('img src=ajax-loader.gif', 
function() {
               });
               setTimeout(function() {
               $('#loading').remove();
               }, 5000);
               });
</script>
<style type="text/css">
html, body{
                 height: auto;
                 margin : 0;
                 padding : 0;
                 }
                 #spanner{
                 width: 100%;
                 height: 50%;
                 margin-top: -100px;
                 clear: both;
                 }
                 #wrapper{
                 text-align : center;
                 }
</style>
</head>
<body>
<div id="spanner"></div>
<div id="wrapper">
<div id="loading" class="wrapper">
[img]ajax-loader.gif[/img]
</div>
</div>
<div id="contentArea">
<iframe name="viewFrame" id="viewFrame" src="default.asp" border="0" 
frameborder="0"></iframe>
</div>
</body>