posted 5 years ago
The 500 page and also the 404 page are pages that are displayed when an exceptional condition is handled by the webapp server itself. In the case of the 404 page, the URL cannot be resolved at all ("Page not found").
The default forms (more precisely the templates) of these pages are actually hard-coded into the webapp server. However you can override them and design your own error pages which you then indicate in your webapps' web.xml config file.
You'd do that mostly as a vanity thing, though, since a well-designed webapp shouldn't be relying on error pages as part of the basic program design. But for people who fat-finger manual URLs you might want some cute alternative 404 page.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.