If you have namespaces, you need to map a prefix in the stylesheet:
@namespace prefix url(value);
For example, my tideinfo service namespace:
@namespace t url(http://www.smallx.com/services/tideinfo/2005);
Since ':' (colon) is taken for pseudo classes, the '|' (vertical bar) is use to separate prefix from local name:
t|tideinfo { display: block; }