Create custom 401 and 403 error pages with any WordPress theme without writing a single line of code, set it up and forget it.

With this simple plugin you can assign custom pages (with custom content etc.) as error pages. This works for 404 (page not found) and 403 (forbidden/permission denied).

Site protection plugin for dev instances to avoid indexing by search engines. Doesn't allow access to the site without being logged-in.

Instead of serving a 404 Not Found error with the 404.php template, send a 403 Forbidden error and set $wp_query->is_403 and load 403.php if it exists.