A Responsive Website is one that adapts to various mobile devices, like an iPhone, Android, tablet, etc. In the recent past, having a Responsive or mobile-friendly website was a luxury, however now it is a necessity. Google and other search engines are actually penalizing your website if it is non-responsive. This means that not only are your customers having a hard time navigating your site on their device, but you may not be showing up in search results.