CodeIgniter 404 Page Not Found. (because of space character in project Url)

Most likely CI isn't converting the %20 entity back into a space. It's just best to never use spaces in file/dir names. No OS really likes it. You end up having to put quotes around paths with spaces in them, etc., and different OS's have different means to do that. So if you want consistency across platforms, just don't use spaces and it will work everywhere.