A Simple, Responsive CSS Framework – Base
Base is a really simple CSS framework for building responsive websites that work well in all devices.
It comes with custom styles for headings, tables, blockquotes forms, lists and more.
There is a 960px (max), 12-column grid and it is created with screen readers in mind.
The CSS rules are well-commented and supports all major browsers (IE7+).
Compatibility: All Major Browsers