ThemeForest - Broken 404 - Custom Error Page - RIP | 69,5 KB
This theme is an error 404 custom page (HTML) and has a responsive layout that uses a user helper instead of site links, which guides users by asking some questions. With this feature, not only you can guide users to a good direction but also you can introduce your website to them. You can Add questions/answers in a simplest way as described in the documentaion.
DEMO:
http://themeforest.net/item/broken-404-custom-error-page/5507947