This book is about two phenomena in the world of contemporary web design and web development, RWD and RESS. RWD stands for Responsive Web Design and RESS means RWD with Server Side Components. Both are based on attempts to find a way to deliver content to multiple devices more easily, and efficiently while reducing development time and keeping application and data structures maintainable. The RWD concept appeared first in 2010 in an article by Ethan Marcotte (available at http://alistapart.com/article/responsive-web-design). He presented an approach that allows us to progressively enhance page design within different viewing contexts with the help of fluid grids, flexible images, and media queries. This approach was opposed to the one that separates websites geared toward specific devices. Instead of two or more websites (desktop and mobile), we could have one that adapts to all devices. The technical foundation of RWD (as proposed in Marcotte's article) consists of three things, fluid grids, flexible images, and media queries.

Illustration: Fluid (and responsive) grid adapts to device using both column width and column count

Fluid grid is basically nothing more than a concept of dividing the monitor width into modular columns, often accompanied by some kind of a CSS framework (some of the best-known examples were the 960 grid system, blueprint, pure, 1140px grid, and elastic), that is, a base stylesheet that simplifies and standardizes writing website-specific CSS. What makes it fluid is the use of relative measurements like %, em, or rem. With changing the screen (or the window), the number of these columns changes (thanks to CSS statements enclosed in media queries). This allows us to adjust the design layout to device capabilities (screen width and pixel density in particular).

Images in such a layout become fluid by using a simple technique of setting width, x% or max-width, 100% in CSS, which causes the image to scale proportionally.

With those two methods and a little help from media queries, one can radically change the page layout and handle this enormous, up to 800 percent, difference between the thinnest and the widest screen (WQXGA's 2560px/iPhone's 320px). This is a big step forward and a good base to start creating One Web, that is, to use one URL to deliver content to all the devices. Unfortunately, that is not enough to achieve results that would provide an equally great experience and fast loading websites for everybody.