CSS, the layout and formatting language of the Web, is hard for many people to use. Sass is one of several CSS supersets and/or replacements that have emerged over the years, allowing us to write our CSS more expressively and concisely. In this talk, Hugo Giraudel describes many of the Sass mistakes that he has seen, and corrected, in numerous open-source projects over the last few years — and thus, indicates ways in which you can improve your use of Sass, and thus clean up your stylesheets.