In web design, an approach that adapts the layout of a web application to the viewing environment, e.g. device screen size and orientation. Popular libraries like Bootstrap control content rendering based on layout grids while languages like CSS can apply various styles to the markup. The ASP.NET MVC and the Bootstrap frontend framework in Sitefinity enable you to build and develop apps that are responsive, mobile-first and work seamlessly on any device, desktop or mobile. All MVC widgets are built with a mobile-first mindset.