Responsive design refers to the automatic formatting of webpages so that they are easily viewable and navigable on any kind of device. These days it is no longer a given that people will browse the internet on desktop computers. There is a larger variety of devices including smartphones, tablets and laptops, each of which come with various dimensions of size. Enabling your site to be just as easily navigated by a visitor on these smaller devices, as when they are eon a desktop computer is a big win for SEO.

Why Responsive Design Makes Sense
More consumers are seeking information on products and brands on their handheld devices than on any other platform. This means that if your site is not suitably adaptable to this use you may be missing out on an important revenue stream. Many people that access a site and discover it is difficult to navigate on their devices will seek out an alternative website that is better equipped of their use The goal of SEO is to drive traffic to a website, and failing to utilize responsive deign will mean losing out on the desired visitor numbers.
Another reason this design matters is that Google favors it. while the search engine is yet to make it a requirement, the fact that it has recommended the use of this formatting means that you are more likely to enjoy better ranking if you follow this recommendation than if not. Google is still basically the standard by which we make SEO decisions so following their recommendations can only do you and site good. It is also believed that responsive design makes it easier for search engines like Google to analyze and index the content of webpages.
For those who opt to create a mobile version of their website rather than adopt responsive design, there are several downsides. One is that you have to create a new URL and HTML code. This means you lose what used to identify your webpages, and your mobile version of the site loses the ranking you already have. It is as though you are building an entirely new website and have to work on building rank all over again, even if it is with the same content. You lose all the authority you have built up online when people opt to access your mobile website on their handheld devices. With responsive design however, you get to retain your authority fully and do not suffer at all in the rankings.
Mobile versions also tend to offer more limited content and links to other webpages, as compared to when you look at the desktop versions. This means that even if a person accessing the mobile site on their phone may find what they need, they are less inclined to click on links that will allow them to further explore the website. Search engines like Google tend to note how much visitors to websites spend on the site and explore other content. If they take to spending the minimum amount of time without clicking through to other webpages, it can be detrimental to your trying to build rank.
Ultimately, responsive design helps to not only preserve the ranking of a website, but also enhances user experience. The more comfortable a person using their smartphone or tablet are in navigating your website and finding the content they want. The more likely they are to keep coming back and ultimately enhance your image as a useful resource to search engines. With more and more online users making the switch to mobile devices, it is time to adapt and ensure your website cashes in on responsive design as early as possible.