Вот так тоже работает:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="ru" lang="ru" dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<script type="text/javascript" src="http://yandex.st/jquery/1.4.4/jquery.min.js"></script>
<script type="text/javascript" src="http://hostjs-mybb2011.narod.ru/js/jQuery.ajax.js"></script>
<script type="text/javascript">
$.get('http://nbrb.by/Services/XmlExRates.aspx?ondate=01/31/2011', function(res){
$("#outdiv").append(res.responseText);
});
</script>
<style type="text/css">
body {margin:50px;}
#outdiv {
width: 500px;
margin: 0 auto;
padding: 10px;
border: 1px solid #E9E9E9;
}
</style>
</head>
<body>
<div id="outdiv"></div>
</body>
</html>