Responsive Web Designing

Responsive web design (RWD) is an approach to web design with a strong emphasis on image viewing experience to make reading easier and minimize resizing, panning, and scrolling for simpler navigation. This common set of best user experience practices can be applied to a wide range of devices, including mobile phones and desktop computers.

Mobile first, unobtrusive JavaScript, and progressive enhancement

"Mobile first", unobtrusive JavaScript, and progressive enhancement are related concepts that predate RWD. Browsers of basic mobile phones do not understand JavaScript or media queries, so a recommended practice is to create a basic web site and enhance it for smart phones and PCs, rather than rely on graceful degradation to make a complex, image-heavy site work on mobile phones.

Progressive enhancement based on browser-, device-, or feature-detection

Where a web site must support basic mobile devices that lack JavaScript, browser ("user agent") detection (also called "browser sniffing"), and mobile device detection are two ways of deducing if certain HTML and CSS features are supported (as a basis for progressive enhancement)—however, these methods are not completely reliable unless used in conjunction with a device capabilities database

Bootstrap

Bootstrap is the most popular HTML, CSS, and JS framework for developing responsive, mobile first projects on the web.