Thank you for that and for the reference to css_howto.asp
It is the answer I've been seeking all along and makes obvious perfect sense.
It's something I should have known but having no formal training…
I am still curious though as to why it was necessary to create spry_custom.css when those rules could more easily (my opinion) been included in Accordion.css.
Looking at all the other css files I can see the logic of their separate nature.