Thanks Dave,
So, I'm pretty sure I know what you mean here but just in case, I googled (ok live searched) for an example. Hard to believe (ok, not that hard) but I found myself asking the same question about 18 months ago. Arg. Brain freeze is the only excuse. So, I decided best to blog the answer and maybe I'll remember it longer this time.
Thanks again for the tip.
http://peterkellner.net/2008/05/25/codecampwebsiteseries3/