I'm assuming your virtual hosts document root points to app/webroot
so your links to the css files need to point to /css/file.css
. The way you have it now it's actually looking for app/webroot/app/webroot/css
and that's why you get a 404.
Either that or your .htaccess is wrong or you stylesheet doesn't actually exist. Let me know if this helps and i can update my answer if needed.