Asset folder in root inaccessible

[eluser]Chromana[/eluser]
I'm setting up a new website and trying to make it better than my previous COdeIgniter efforts.
I'm putting an asset folder in root, as described by this post http://ellislab.com/forums/viewthread/66887/#334093 i.e. at the same level as index.php and the system folder.
I am using the following in files:

Code:

<base href="<?php echo $this->config->item('base_url') ?>asset/" />
<link rel="stylesheet" href="css/base.css" type="text/css" />

However, I get a 404 for www.mysite.com/asset/css/base.css and also just for www.mysite.com/asset/.
Do I need to add something to routes to get this to work? At the moment I just have the default of:

Code:

$route['default_controller'] = "ctrl_main";
$route['404_override'] = '';

I get a 404 for any file in the asset folder. How do I fix this?
Many thanks!