Add path to css and images

[eluser]Unknown[/eluser]
Hello , i problem with css and images files.

I create directory css in first path ... system , application , css ...

In my layout
I set:

<link rel="stylesheet" href="<?php echo base_url() ."css/main.css" ?>" type="text/css" />

and this not working.

My config file.

$config['base_url'] ='http://site.com/ci/';
$config['index_page'] = 'index.php';

I change index_page to '' , and not working too.

I problem with images too.

Please help me for this .

Thanks you.