Temporary Maintenance - this will block users who are NOT an administrator from viewing the website.

function.php

function wp_maintenance_mode(){

if(!current_user_can(‘edit_themes’) || !is_user_logged_in()){
wp_die(‘Maintenance, please come back soon.’, ‘Maintenance – please come back soon.’, array(‘response’ => ’503′));
}

}

add_action(‘get_header’, ‘wp_maintenance_mode’);