If you don’t have a mobile-friendly site, it will likely affect your Google search ranking adversely starting April 21.

Google Webmaster Central says:

“Starting April 21, we will be expanding our use of mobile-friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results. Consequently, users will find it easier to get relevant, high quality search results that are optimized for their devices.”

The change has the potential to affect site rankings as much or more than Google’s previous Penguin and Panda updates.

Google offers some advice on how to prevent this with its guide to mobile friendly sites (https://developers.google.com/webmasters/mobile-sites/get-started/?utm_source=wmc-blog&utm_medium=referral&utm_campaign=mobile-friendly) and a mobile-friendly test, (https://www.google.com/webmasters/tools/mobile-friendly/?utm_source=wmc-blog&utm_medium=referral&utm_campaign=mobile-friendly) among other tools.

For the full story see Google Webmaster Central: http://googlewebmastercentral.blogspot.com/2015/02/finding-more-mobile-friendly-search.html