Codeigniter shared hosting 404 error

The most common reason why "it works on localhost, but gives 404 on the live site" is a failure to follow CodeIgniter's file naming requirements.

1. The first character in the file names of Controllers, Libraries, and Models MUST be uppercase
   
2. All other characters in the file name must be lowercase
   
3. File names and Class names must be exactly the same
   

This happens a lot to devs where localhost is no a Windows system and the live server is Linux. The first OS is a case-insensitive, but the later is case-sensitive.