How to create a 404 page in CodeIgniter

This post is about creating a custom 404 page in CodeIgniter. There are so many reasons for having 404 page. Because you cannot avoid user typing incorrect URL pointing to a page on your domain which doesn't exists. Also there is some website can link to some url on website which no longer valid. Codeigniter provides it's own 404 page which is ok. But we can create our own custom 404 page.CodeIgniter provides an easy way to build a custom 404 (Page-not-found) page. Here is the step by step on setting up a 404...