Web design today is different than it was even just a few years ago. The explosion in popularity of mobile devices such as smartphones and tablets have dramatically changed where and how people experience the web.
The freedom of these types of wireless devices means people can access your site from virtually anywhere, and at anytime, but the variety of different screen sizes and methods of interfacing with your site also pose new challenges. If your site isn't optimized to be viewed on mobile devices, let alone to be navigated via touch, I'll bet dollars to donuts that your site's mobile experience probably isn't very pleasant.
