Change it into the following code

<!--{if $loggedin == "ja"}-->
<!--{$message}--><!--{$loggedin}-->
<form action="index.php" method="post" name="uitlog">
<input type="hidden" name="actie" value="uitloggen" />
<input type="submit" value="uitloggen" />
</form>


<!--{else}-->
<!--{$message}--><!--{$loggedin}-->
<form action="index.php" method="post" name="login_form" action="index.php">
<input type="hidden" name="actie" value="inloggen" />
<input type="text" name="username" value="username" />
<input type="password" name="password" value="password" />

<input type="submit" value="inloggen" />

</form>


<!--{/if}-->