The increasing number of website visitor that using mobile device is really high nowadays until on 21st April 2015 google announce will using mobile friendly website as one of many ranking signal on google search engine, it will effect your google ranking on mobile device search only (the desktop search result will not taking effect on it). With mobile friendly website or also known as responsive webdesign, website will adjusting the design to the specific device so it will be more better in user experiences that will make your visitor more comfort in exploring the information on your website.
Imagine a user looking at your site on a mobile device. Can the user easily read your page and find the necessary information or is too hard to use?
The desktop version of a site might be difficult to view and use on a mobile device. The version that's not mobile-friendly requires the user to pinch or zoom in order to read the content. Users find this a frustrating experience and are likely to abandon the site. Alternatively, the mobile-friendly version is readable and immediately usable.
To check neither your website is mobile friendly you can visit this linkhttps://www.google.com/webmasters/tools/mobile-friendly/
Below are an example mobile friendly check on www.ilzicorp.com