A site layout example that adapts to browser viewport width was first demonstrated by CameronAdams in 2004. By 2008, a number of related terms such as "flexible", "liquid", "fluid", and "elastic" were being used to describe layouts. CSS-3 media queries were almost ready for prime time in late 2008/early 2009. Ethan Marcotte coined the term responsive web design  (RWD)—and defined it to mean fluid grid/ flexible images/ media queries—in a May 2010 article in A List Apart. He described the theory and practice of responsive web design in his brief 2011 book titled Responsive Web Design. http://en.wikipedia.org/wiki/Responsive_web_design
- Sept'2014 (using BootStrap v3) http://www.sitepoint.com/responsive-web-design-tips-bootstrap-css/
- follow-up on its 12-grid-system
- Aug'2013 (using BootStrap v2.3.2) http://www.sitepoint.com/building-responsive-websites-using-twitter-bootstrap/
A key requirement to be a Progressive Web App.
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