Look around you, Mobile Phones, especially Smart Phones have become part of everyday lives. We use them to communicate, socialise, make purchases, play games, and much more.
The phone has gone from just making voice calls to a camera, music center, receiving emails on the go, communicating face to face and as a means to surf the Internet.
Now you have to remember that a Desktop Computer Screen is much bigger than a phone screen – you want your Web Site to open up on Mobile Phones, Small and Big Tablets, as well as Desktop Computers and you want the experience to be the same across all screen sizes, and you do not want to go to the expense of crating a second Mobi site for Mobile Screens.
The solution is Responsive Deign. This allows a Web Site to scale across different Screen Sizes, from the Biggest to the Smallest. An example of the can be seen here – go on, view it on your phone and on your Desktop.