You can do it with a frameset and the adress bar won't change, no matter where users navigate to.
But as already mentioned, even Internet Explorer -since IE7- focuses on the User to prevent stuff like that, the User has the right to know where he is surfing to - it is a security issue.
Imagine you come to some website that looks clean and friendly and the Site redirects you to an array of phishing sites without you or your browser security noticing it. The Site owner could get all your private info, for e.g. your clipboard content or geolocation data and while you are at ease, the Site owner empties your bank account. Just an example.
In addition to your below answer I tried window.location.href on Firefox 3.6 and it works as expected.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>urlRefresh</title>
</head>
<body>
<input type="button" value="changeAdress" id="changeAdress" />
<script>
document.getElementById('getValues').onclick = function() {
window.location.href = "http://www.bing.com";
}
</script>
</body>
</html>
If you click the button changeAdress JavaScript issues a GET Request via your browser to the desired Website.
See http://plixi.com/p/46770650