Insulating part of a HTML document from global CSS

Hey everyone,

I tried searching online for this, but came up empty, so I'll ask here. Are
there any plans to provide a mechanism for insulating part of a HTML node
tree from globally defined CSS styles? The classic example is the case of a
web-based email client. Emails contain their own style sheets and HTML, but
how is one meant to display this within the context of another web page
without resorting to iframe's. I don't see iframe's as solution as they
come with scripting, security and usability limitations.

Has any thought been put into this?

Cheers,
Tom