I added these custom js and css file:

1. `skin/frontend/base/default/black/NewsletterPopup/js/main.js`
2. `skin/frontend/base/default/black/NewsletterPopup/css/main.js`

Then I included them via my modules layout file

> 
> app/design/frontend/base/default/layout/black/newsletter\_popup.phtml
> 
> 
> 

```
<?xml version="1.0"?>
<layout version="0.1.0">
    <default>
        <reference name="head">
            <action method="addJs">
                <script>black/NewsletterPopup/js/main.js</script>
            </action>
            <action method="addCss">
                <stylesheet>black/NewsletterPopup/css/main.css</stylesheet>
            </action>
        </reference>
    </default>
<!-- ... -->

```

But a network analysis showed that the files could not be found and if I enter the link to the file directly into the URL then the "*404 Sorry page not found*" page shows up.

What am I doing wrong?