You are working on a site and using a CSS framework like bootstrap or foundation or anything else and for some reason you wanted to add 10px padding at the bottom and 20px margin at the right to a HTML tag, now with rules.css file added in your project you can use the pre-defined classes with the HTML tag, which will save your development time and also helps you to reduce CSS redundancy, project is on github: https://github.com/rakibtg/rules.css
any criticism is welcome :)