404 page

A 404 page is what a user sees when they try to reach a non-existent page on your site (because they’ve clicked on a broken link, the page has been deleted, or they’ve mistyped a URL).

To set up 404.html page on your server add this to the .htaccess file:

ErrorDocument 404 http://www.domain.com/404page.html

Thats it !

For more detailed instructions please look following article.