Anna Ullrich just published an excellent article called Who’s Editing Your CSS? explaining how Expression Web 2 handles CSS and why you can trust the program to spit out proper non-bloated code.
If you’ve watched my webcast or read any of my articles you should have an idea of this but Anna’s article is far more thorough than anything else I’ve read.
Oh, by the way Anna: Who is editing your CSS? Your page is broken in Opera ;o)