A Fluid CSS Grid System – Extra Strength Responsive Grids
Extra Strength Responsive Grids is a CSS framework that comes with solutions to various issues experienced in responsive layouts.
The framework is completely grid-focused (no styles for typography, tables, forms, etc.) and uses percentage-based width adjustments.
For smaller screens, besides using less columns, elements can be resized smartly.
Also, it has support for nested grids and the framework is built on top of SASS that allows any quick customizations.