Google is beginning to crack down on websites that do not display properly on mobile devices. A ‘mobile-friendly’ tag will be added to search engine results on mobile devices in the coming weeks.
Websites will only be regarded as mobile friendly if they use a responsive design, avoid non-standard software such as Flash and space links far enough apart to be easily tapped on touch screen devices.
Google has also announced that it is experimenting with using these criteria as a ranking signal (i.e. penalising non-mobile-friendly webpages).
This is just another example of why it is important that we use responsive, mobile-friendly designs from now on.