More often than not, the mobile experience for a Web application or site is designed and built after the PC version is complete. Here's three reasons why Web applications should be designed for mobile first instead.1. Mobile is exploding Though the Web has been accessible on mobile devices for years, today's smart phones are driving huge use of networked applications and Web content. Consider that AT&T, the exclusive carrier for Apple's iPhone, has seen a 4,932% increase in mobile traffic data i