UIkit
Lightweight modular front-end framework for developing web interfaces
...To use UIkit's CSS and JavaScript, include the files in your own HTML and then create the markup of any of the components. When you have installed UIkit with Less sources, you can compile it and add your own custom theme. Less is the language that the UIkit styles are written in. This allows you to include customizations in the build process, rather than manually overwriting a lot of CSS rules by hand.