Mobile Friendly Responsive Web Design
Google has decided that as over 50% of search queries come from Tablet and Mobile; Google will reflect search results within these small devices. After all, there is nothing worse than seeing a website that isn't built for small devices. The upshot is that if your website isn't mobile friendly (i.e shrinks automatically to fit the width of the screen in a column view), then it will not be shown to the viewer within search results through tablet or mobile.