Just how attached are consumers to their smartphones? A 2012 study by IDC Research reported that 72% of all smartphone users say their devices are within an arm's reach for at least 23 hours a day. That's about 89 million adults maintaining a nearly constant connection. And when we observe kids under 18, it's even more obvious that mobile is engrained in our culture.

That cultural shift shows up everywhere:

• 79% of all smartphone users reach for their phone within 15 minutes of waking up, according to the same 2012 IDC Research study.

• A November 2013 study by Deloitte says nearly seven out of 10 smartphone and tablet users were expected to use their devices to research, shop and buy online during this past holiday shopping season—a total of about 95 million users.

• Within the financial services industry, smartphones are now the most common starting point for banking activity, according to a 2012 multi-screen user behavior study by Google & Ipsos.

Day after day, new studies confirm that mobile is winning in both convenience and experience. Not surprisingly, as the mobile culture grows and devices become more powerful, consumers expect better online experiences. That's exactly why responsive design—a way to optimize websites for literally any device—is becoming such a key component to effective online marketing.

Responsive design works by taking cues from the user's device. It looks at things like screen resolution and browser width and automatically adapts content on the fly. It also adds more functionality, features and convenience (like click-to-call) when it makes sense. The result is a more enjoyable experience that deeply engages the audience.