Print design has the physical constraint of the canvas. The format is fixed. The situation is different on the web. We can’t know in advance exactly how someone will view our sites. We don’t have a fixed canvas. We need to create websites with the ability to adapt and respond.
Designing for the web means being open to the flexible nature of the web. We need to develop flexibly so our sites work well and look good across a range of devices and device characteristics. These are the ideas behind responsive design.
How To Build A Responsive site
Article source: http://www.vanseodesign.com/web-design/responsive-workflow/