Responsive Web design (RWD) is a Web design methodology aimed at crafting sites to provide an optimal viewing experience – easy reading and navigation with a minimum of resizing, panning, and scrolling – across a wide range of devices (from mobile phones to desktop computer monitors). A site designed with RWD adapts the layout to the viewing environment by using fluid, proportion-based grids, flexible images and CSS3 media queries, an extension of the @media rule.
Non-responsive versus responsive redesign example