Not many people know about the loneliness of the Front End Developer (FED;). However, it's a fact that many projects will have an array of programmers but only one soul FED.
For those that don't know, responsive web design is "simply" a design that changes to fit the size of the browser window. This really does change everything, as it is an extension of the "one web for all" paradigm that has been a guiding light of the web since it's inception. Your desktop website scales to become your mobile website. The same website, presented differently. Thank you, Ethan Marcotte.
So know, in the words of Chris "Whenever I see a new website, I give it a wiggle"!
Plenty has been written about this subject, and it's in the same world-wobbling mould-break as Jeffrey Zeldman's Designing With Web Standards, so I'll be writing plenty more about it too.
My recommendation? Buy the book!.