FireSass is a Firebug extension that makes Firebug display the Sass filenames and line numbers of Sass-generated CSS styles rather than those of the generated CSS. Usage First, install FireSass from this page. Second, enable Sass's :debug_info option. If you're using Sass with a Ruby web framework, you probably want to set Sass::Plugin.options[:debug_info] = true. Add this to config/environment.rb