->Specification：http://www.foundcss.com/
->Source code：
Foundation 是一個易用、強大而且靈活的響應式前端框架，用於構建基於任何設備上的響應式網站、 Web應用和電子郵件。結構語義化、移動設備優先、完全可定製。
Foundation is written in Sass, which allows us to make the codebase customizable and flexible.
Foundation for Sites can be compiled with Ruby Sass and libsass.
The flex grid is only supported in Chrome, Firefox, Safari 6+, IE10+, iOS 7+, and Android 4.4+. Flexbox is supported in Android 2, but not reliably enough for use with this grid.