Server specific settings in web.config / Nested Comments i..

I'm trying to configure a web.config that has different settings on different
servers. (Staging versus live.)

My research indicated that there might be "site" and "machine" tags in
web.config that did this. Unfortunately they are not recognised by Visual
Studio 2008. (And neither is there an obvious alternative.) I did get a
message that it was possible but the poster didn't reply when I asked exactly
how it was done.

So I've written off that approach and am using comments to do half a job for
this.

Unfortunately comments in xml can't be nested so I tested the <![IGNORE[
directive which is part of XML. It allows nested comments but unfortunately
IIS 6 barfs when it sees it and crashes the web site!!

Is there a way to do this?

(NOTE: I have recently moved away from custom config handlers and am trying
the "out of the box" functionality, so I'm not asking about answers that
involve writing my own handlers!)

(Side note: I've found it impossible to post to these newsgroups via the
web interface for several weeks using IE. I'm currently using Firefox which
after multiple complaints about not finding cpmsftibpro01.dns.microsoft.com,
seems to have got through. Anyone got insight on what's failing?)