As you can see, mobile phones overtook desktops five years ago and now stands at 54% compared to desktops at 43% and tablets bringing up the rear at 3%.
Clearly, it’s extremely important that your website looks good on a mobile phone. Add to this the fact that when Google crawls the web to builds its ranking for search results, it now primarily uses the mobile phone view of your website. If the mobile phone view is poor or incomplete, then your site will be penalized in the ranking.