When I started developing websites professionally 16 years ago, I only had to worry about a couple of screen sizes. Most monitors came in roughly the same size and we didn't have to even think about phones.

Now, we have so many devices to plan for that when you develop a website you're managing multiple breakpoints.

But if you haven't made the switch to mobile-first design yet, you're at the risk of being behind a pretty big curve.

Designing mobile first isn't just about following the industry's trends, either. Let me walk you through five big reasons why you should be designing and developing websites mobile-first.