SCSS is one of the two syntaxes available for Sass - a CSS preprocessing language. This article talks about the different Sass syntax and the difference.
The problem: HTML elements have inconsistent sizes across different browsers. The solution: Set box-sizing for all elements to border-box. A long-time bane for web developers, Internet Explorer did one thing right: It sized boxes properly. Other browsers only look at the content when calculating the width of an HTML element, with everything else treated as surplus. A width: 200px div, with 20px padding and a 2px border, renders as 242 pixels wide.