responsive design

Responsive Web Design (RWD) essentially indicates that a web site is crafted to use Cascading Style Sheets 3 media queries, an extension of the @media rule , with fluid proportion-based grids (which use percentages and EMs instead of pixels) , to adapt the layout to the viewing environment, and probably also use flexible images. As a result, users across a broad range of devices and browsers will have access to a single source of content, laid out so as to be easy to read and navigate with a minimum of resizing, panning, and scrolling. "Mobile First" and "Progressive Enhancement / Unobtrusive JavaScript" (strategies for when a new site design is being considered) are related concepts that predated RWD: browsers of basic mobile phones do not understand media queries or Javascript, and it is wise to create a basic web site then enhance it for smart phones and PCs ‐ rather than attempt "graceful degradation" to try to degrade a complex, image-heavy site to work on the most basic mobile phones. Browser detection and mobile device detection are two ways of deducing if Javascript and certain HTML and CSS features are supported, however Javascript libraries like Modernizr, jQuery, and jQuery Mobile that directly test for features/user agents are also popular. (Excerpt from Wikipedia article: Responsive design)