Bourbon Neat is a CSS framework that uses the CSS pre-processor SASS to create semantic, fluid grid layouts for your responsive websites.

Columnal:Columnal is a responsive CSS grid system for both desktop and mobile browsers. The Columnal grid system has a built-in debugging CSS to display the structure of the pages being built.

Tailwind packs a lot of power into a memorable and concise syntax, making it a fast-rising alternative to the likes of Bootstrap and Foundation.

Pure CSS is a modular, responsive framework that puts its own spin on CSS development, with an approach that is minimal, lightweight, and yet comprehensive.

Well, with simple CSS, the fluid grids help to create some awesome photoshop style layouts that can be custom according to your choice. BOOTSTRAP is the framework that facilitates the prototyping.