Guil Hernandez
Guil is the front-end design teacher at Treehouse. You can follow Guil on Twitter at @guilh.
CSS Tip: A Better Clearfix with Sass
CSS Tip: Better Rounded Borders
Triggering CSS Animations with Sibling Selectors
Extending Placeholder Selectors with Sass
Take Control of the Box Model with box-sizing
Create a Themable Button Set with Sass
5 Useful CSS Selectors
CSS3 Substring Matching Attribute Selectors
How to Choose the Right CSS Preprocessor
HSLa Color Values in CSS - Quick Tip