entonces te falta una al final
<?php
//Comprobamos que el usuario ha iniciado sesion con una contraseÒa valida
if($_SESSION[authuser]!=1) {
echo 'you are not allowed to view this page, you can register by clicking ';
echo '<a href="register.php">here</a>';
exit();
}
?>
<HTML>
<head>
<title>
<?php
if(isset($_GET['FAVMOVIE']))
{ esta no la cierras
echo ' - ';
echo $_GET ['FAVMOVIE'];
?>
</title>
</head>
<body>
<?php include 'header.php';
?>
<?php
function listmovies_1() {
echo '1. The lord of the rings <br>';
echo '2. Grand Torisno <br>';
echo '3. The godfather <br>';
echo '4. hiden trace <br>';
echo '5. Man on fire <br>';
}
function listmovies_2() {
echo '6. The karate kid (2010 version) <br>';
echo '7. The prince of persia <br>';
echo '8. Pirates of the caribean <br>';
echo '9. Open hurt <br>';
echo '10. Seducing a Stranger <br>';
}
if (isset ($_GET ['FAVMOVIE'])) {
echo 'Welcome to our site.';
echo $_SESSION['username'];
echo '<br>';
$movierate = 7;
echo 'Mi personal rate for this movie is ';
echo $movierate;
} else {
echo 'My top';
echo $_GET['movienum'];
echo 'movies are';
echo '<br>';
listmovies_1();
if ($_GET['movienum'] == 10) {
listmovies_2();
}
}
?>
</body>
</HTML>