Fluidity
Profound Grid | A grid system for fixed and fluid layouts
Another take on grids
Responsive background images with fixed or fluid aspect ratios – Voormedia
What's the easiest way to scale background images in responsive layouts? We use an old technique and enhance it to fluidly change the aspect ratio of background images.
Fully fluid, responsive CSS carousel
20 Useful Tools for Responsive Web Design
21 Top Tools For Responsive Web Design