Custom error pages are used to present a friendly, branded message to visitors and help guide them to related pages or alert them of the error.
Marketpath CMS provides the ability to create completely custom error pages for various HTTP status codes and utilize regular expression matching by URL and path. Errors can occur based on simple errors, such as "404 Page Not Found", or more complex 5xx errors resulting from errors in template markup.
Speaking of great error pages, here's a list of some of the best custom 404 pages: http://www.creativebloq.com/web-design/best-404-pages-812505
As a beta user you'll pay nothing until your site is live and have immediate lifetime access to all new features released during the beta. When you go-live during the beta, you'll get the benefit of a reduced monthly fee for all the same features you've been using.