CoreSheet is a solid open source CSS framework for front-end web developers. It is completely customizable and comes with a set of styled HTML components. It provides a percentage-based responsive grid system and gives developers full control over the design settings.
CoreSheet is a modern framework so it works perfectly in modern browsers. It relies on CSS3 so there is a wide range of supported browsers: Internet Explorer 9+, Edge, Firefox, Chrome, Opera and Safari as well as mobile browsers on iOS, Android and Windows Phones. CoreSheet is well tested and has a lightweight footprint of 32 KB (minified). It's also available as package via NPM and Bower.