Frankly between the two of us, while I do see the merits in designing a mobile website first — in terms of a website’s information architecture as well as the aesthetic appeal, especially for the sake of its usability and appearance on a small screen — I’m not sold yet on whether a mobile site has to be designed first. That said, it does need to be designed at the same time. Semantics, eh? I’m hilarious, I know. But thanks for thinking it.
So what’s this “mobile first with a twist” schtick? Basically it’s a bunch of borrowed idea’s from Ethan Marcotte’s amazing little book, Responsive Web Design, Luke Wroblewski’s “equally” little book, Mobile First, (by the way, me calling each author’s book “little” isn’t a slight in the least, both book’s strength lie in their size, and that’s the point) and something I’m sure Harry Roberts wrote a little while ago but I can’t relocate now. About designing for less capable browsers first then adding on top of that base for more capable browsers — or specifically how such an approach plays with Internet Explorer 8 and below.
Anyway the “mobile first with a twist” approach is quite simply a matter of designing a website for mobile, meaning for small screens (not just visually but functionally too), then tweak it larger, with the least amount of effort and the most basic — yet responsive — CSS possible. This as your starting point. A base from which to build. The thinking is this is what a visitor will see and use who is using a less capable web browser. Read “Mobile first with a twist” in its entirety