There are a lot of different ideologies when it comes to mobile web development, responsive web design, a separate domain serving a mobile specific design and content. I just came across an boilerplate from Andy Clarke called ‘320 and Up‘ which starts with the smallest screen size, then becomes responsive as it grows. The benefit of this method is it forces the developer to focus on the main reasons why a user will come to the site first, then add in the non mission critical content as the screen will allow it.
It will allow designs to be more easily optimized for size and speed. Responsive web design is the practice of creating a site that will stretch and flow to fill the screen available, images are large by default then scaled back through CSS. If you are forced to design for the smallest size first, the images served to that device will be much smaller. Check it out - 320 and Up