The renderkit docs specify StykesheetRenderer directly renders the request path
gotten from Resource.getRequestPath(), when it should pass through
ExternalContext.encodeResourceURL() taking into account portlets.
the change has been done in implemetation (Mojarra) see:

https://javaserverfaces.dev.java.net/issues/show_bug.cgi?id=1860

Environment

Operating System: All
Platform: Macintosh

Affected Versions

[2.1]