Less (http://incident57.com/less; which you’ll read about in Part III of this book) is a CSS framework that allows you to more efficiently create CSS. In addition to allowing you to set variables and “mixins” for colors, fonts, etc. directly in your stylesheets that can be called anywhere else in the stylesheets, it allows you to nest styles within each other. For example, a simple navigation menu might look like this:

ul#navigation { list-style: none; display: inline; }
ul#navigation > li { list-style: none; float: left; margin-right: 1em; 
    border-right: 1px solid gray; }
ul#navigation > li a { padding: 3px 0; color: black; text-decoration: none;}
ul#navigation > li a:hover { color: white; background: black; 
    text-decoration: underline; }