[eluser]CroNiX[/eluser]
Using base_url() won't work if his assets are outside of the site/document root.
And, you can't directly access assets via the URL that aren't in a web accessible space whether using codeigniter or pure HTML. So you'll have to move them within the site, or to a CDN or somewhere else that is web accessible instead of a private dir. Or you could define a directory alias in .htaccess or something as well.