A CSS framework is a pre-prepared library that is meant to allow for easier, more standards-compliant styling of web pages using the Cascading Style Sheets language. Like programming and scripting language libraries, CSS frameworks are usually incorporated as external .css sheets referenced in the HTML . They provide a number of ready-made options for designing and laying out the web page. While many of these frameworks have been published, some authors use them mostly for rapid prototyping, or for learning from, and prefer to 'handcraft' CSS that is appropriate to each published site without the design, maintenance and download overhead of having many unused features in the site's styling

Variable Grid System
BlueTrip: Full Featured CSS Framework