Your code contains a mistake in passing arguments to the wp_login_form()
function. If you define the arguments after function then the function will be called with the default values, so your arguments will not have any effect. The correct code is below:
if (is_user_logged_in()) {
echo '<div class="logout"> <p>Hello!<div class="logout_user"> You are logged in and can proceed to the <a href="http://example.com/seminar">Online Seminar</a>.</div></p><br /><p><a id="wp-submit" class="logout" href="', wp_logout_url(), '" title="Logout">Logout</a></p></div>';
} else {
$args = array(
'echo' => true,
'redirect' => 'http://example.com/seminar',
'label_log_in' => __( 'Log in' ),
'form_id' => 'seminar-login',
'label_username' => __( 'Username' ),
'label_password' => __( 'Password' ),
'label_remember' => __( 'Remember Me' ),
'id_username' => 'user_login',
'id_password' => 'user_pass',
'id_submit' => 'wp-submit',
'remember' => true,
'value_username' => NULL,
'value_remember' => true
);
wp_login_form($args);
}