When I first started creating websites there were no smart phones, no iPads or tablets. It was a simpler online world and often the biggest challenge was browser consistency or Mac vs PC. While those things are still on the check list they are much less of an issue today. What we now have to ensure is responsiveness for different devices, mostly phones.
Responsiveness in a website has become one of the most important functions for today’s website. It ensures your site is mobile friendly (almost 54% of web visits are mobile), looks good on a variety of screen sizes and can help improve your rankings in search engines.
The goal of having a responsive website is to avoid resizing, zooming, panning etc. making the site hard to visit. When the site resizes and adapts to its screen size the user experience is improved and will keep them on the site longer with less frustration.
If you have an older website it may not be responsive and that can be doing your business a disservice. The good news is that all current website platforms available today have this in mind and while you may have to tweak things the majority is already accounted for.