Sometimes the WordPress default error page handling is not enough, because it only shows a simple text or you have to create a custom 404 template with (more) static content.
F4 Error Pages allows you to assign any existing page from your installation to be shown, if a page is not found or the permissions for a request is denied.
So you can create nice and informative error pages with your own content elements or whatever you like, fast, without overhead and unnecessary features.

Usage

After installation you can assign existing pages as error pages. By default there are no pages assigned.
You can access the settings page either if you click the ‘Settings’ link in the plugins list or you can find it directly in the menu (Settings -> Error Pages).

Features overview

Show custom page if requested url is not found (404)
Show custom page if permission is denied (403)
Easy to use
Lightweight and optimized
100% free!