Responsive Web Design
The use of mobile devices to surf the web is growing at an astronomical pace, but unfortunately lots of websites are not optimized for those mobile devices. Mobile devices are often constrained by display size and require a different approach to how content is laid out on screen. That is why you require a designer to make your site responsive so it is automatically compatible with Desktops, Laptops, Tablets, Mobile Devices and also compatable with all browser types.
Responsive web design, originally was developed to responds to the needs of the users and their devices . The layout changes based on the size and capabilities of the device. On a phone, users would see content shown in a single column view and on a tablet it might show the same content in two columns.