404 page not found

Hi there,

I'm receiving the following error. All was well before taking the site live, I even changes the url from localhost to that of my domain on the config file. I have also set the url helper on the autoload file but still receiving the same error. Help me please I'm stuck
 
A PHP Error was encountered
Severity: Error
Message: Call to undefined function base_url()
Filename: html/error_404.php
Line Number: 14
Backtrace: