404 OOPS!
Page not found!
"Sorry, it appears the page you were looking for does not exist anymore or might have been moved.
Please try your luck again."
This is Joomla! Article, You can change text and titile in Article Manager, click the Content → Article Manager menu item and find article Error 404.
If you want select other article you can change article ID in /templates/template-name/error.php