There are options on the server side that can help facilitate this approach. Detecting a mobile platform from the server side can allow you to dish out those tailor made mobile versions without having to rely entirely on stylesheets. It's especially useful to take this approach when trying to minimize bandwidth.
Raises some very interesting points as regards, what we are calling the web these days and how we sucessfully design and development for commerce
Designing multiple layouts for different media - desktop, tablet, mobile is a challenge.