Hi there,
All skins in the directory are cached on by the Google cache - except
skins loaded via the testing mode which deliberately don't use the
cache to make testing possible.
If you are seeing now immediate changes then either something's wrong
with the Google caching period or possibly something else is caching
your skin. Try emptying your browser cache and/or doing a ctrl-f5 to
reload the page. If this does not work then let me know. People would
not have been able to make all these skins without having this feature
working so I'd be grateful if you could post back.
As a workaround you could try appending some meaningless query string
to your css url when you enter it into the gadget settings e.g.
http://domain.com/css/test.css?abc=123.
Cheers