AFLogo selector uses a 'relative url' notation when a 'context relative url' is more desirable.

The skin selector - .AFLogo - defined in simple-desktop.xss defines the property 'background-image' using a relative url notation, as follows

<style selector=".AFLogo">
<property name="background-image">url('../../images/logo-dark.png')</property>

The above usage runs into problems when images along with other resources get hosted on a CDN for example. It's desirable in this case to use a context relative url (as explained here - http://myfaces.apache.org/trinidad/devguide/skinning.html#urls)