The answer is not building a separate website for every platform. That might've been fine when a new platform arrived every few years. But now that they seem to arrive every few weeks, that strategy is untenable. There aren't enough of us to support and design a fresh website for mobile, for tablets (for 7" and for 10" tablets), for television and for speech-based interfaces that are around the corner.
It's a content-strategy nightmare and a voracious resource hog to build and support separate websites for each and every platform, for each and every screen size, for each and every input style (touch, speech, text and so on).
Definitely with a read.