There are a lot of approaches when it comes to web development for
mobile. In the end I believe it comes down to "fitness of purpose." You
have to decide what will be best suited for your audience by looking at
how many mobile users you actually have and how best to serve not just
them but all your users.
Responsive Web Design
A good article from A List Apart about "Responsive Web Design" as it
refers to Mobile.
A media query allows us to target not only certain device classes, but
to actually inspect the physical characteristics of the device
rendering our work. Fluid grids, flexible images, and media queries are
the three technical ingredients for responsive web design, but it also
requires a different way of thinking. Rather than quarantining our
content into disparate, device-specific experiences, we can use media
queries to progressively enhance our work within different viewing
contexts. That's not to say there isn't a business case for separate
sites geared toward specific devices; for example, if the user goals
for your mobile site are more limited in scope than its desktop
equivalent, then serving different content to each might be the best
Authors of "Rethinking
Mobile Web" they give an excellent presentation that turned a lot
heads. The main idea is designing for Mobile first and desktops second.