Basic Principles of Responsive Website design/coding
Responsive website is required to convey the branded website data to the users screen size. Screen size can be any a mobile, a tablet (Landscape and portrait views), a laptop (11inch, 13 inch, 15 inch) and their screens resolution. User can still feel the exact branding of the website.
There are plenty of CSS frameworks available.
The aim of frameworks is to provide a common structure so that developers don’t have to redo it from scratch and can reuse the code provided. Developers suggests suitable frameworks for backend and front end.