Need help about path

Please, put your code inside code blocks and indent it properly, like this:

PHP Code:

public function index()
{
   $this->load->view('index.html');
} 


It's not clear what you want. If you let your users access a URL CI/1, how would your application know which controller/method to call?
I'm not sure whether this route will work:

PHP Code:

$route[':num'] = 'welcome/show/$1'; 


You can also use regular expressions in routes, for more flexibilty.

Remember that routes are always relative to the base_url.
How is your base_url() set in application/config/config.php?