I haven't actually implemented with a framework, but there are all sorts of frameworks (and types) out there. Some are intended to help implement a specific grid layout, others are intended to simplify CSS usage (e.g., for typography), some are to make older browsers HTML5/CSS3 compatible, and still others are for "responsive" layout. They use CSS, Javascript, and even PHP modules. I don't know of any that try to do all these things. Perhaps a "mix 'n' match" building block approach could be whipped up? That might be a fun project for someone -- a framework for a framework.