[PHP] Problème incompréhensible

<form method="post" action="verif.php"><input type="password" name="pass">  
<br /><br /> 
<input type="submit" value="Valider" align="center"> 
</form>

<?php  

$pass = $_POST['pass']; 

if ($pass == "xx") 
{ 

?> 

Blabla mdp ok 

<?php 
} 

else 
{ 
?> 
Code incorrect.<br /> 
<a href="xx" color="red"><b>Retour</b></a> 



<?php 
} 

?>