protected dot php

<html>
<html>
<title>protected web page</title>
</head>
<?php>
session_start();
if($_SESSION['login']!="OK")
{
header('Location:login.html');
exit();
}
?>
<body>
<h1>Protected Web Page</h1>
<?php
echo "<p>you have successfully logged in!</p>";
echo "<p>your username is:";
echo $_SESSION['username'];
echo "<br/>";
echo "your password is:";
echo $_SESSION['password'];
echo "</p>";
?>
<form>
<input class="MyButton" type="button" value="Screen Resolution" onclick="window.location.href='resolution.php'" />
</form>
<form>
<input class="MyButton" type="button" value="Browser Dectection" onclick="window.location.href='browser.php'" />
</form>
<form>
<input class="MyButton" type="button" value="create user" onclick="window.location.href='create_user.php'" />
</form>
<br>
<br>
<form>
<input class="MyButton" type="button" value="Logout" onclick="window.location.href='logout.php'" />
</form>
</body>
</html>