Subdomain does not work for CodeIgniter
Your controller name is Welcome.php
as a public_html/demo/application/controllers/Welcome.php
.
Please change instead Welcome.php
to welcome.php
Set instead $route['default_controller'] = "Welcome"
to $route['default_controller'] = "welcome"
in routes.php
If you have CodeIgniter install in your main domain add RewriteBase / in your .htaccess