In simple terms, a responsive web design figures out what resolution of device it's being served on. Flexible grids then size correctly to fit the screen.

The new Bootstrap 3 promises to be a smaller build. The separate Bootstrap base and responsive.css files have now been merged into one. There is no more fixed grid, only fluid.

Have you ever had a project where you thought it would be so much better to just throw everything out and start over? I believe that’s what’s happening with BS3.

Quasipickle