https://teamtreehouse.com/library/learn-modern-css-layout-techniques
Learn Modern CSS Layout Techniques | Treehouse
Build your CSS skills by learning modern and efficient ways to build responsive page layouts.
css layout techniqueslearnmoderntreehouse
https://www.w3.org/TR/2016/NOTE-WCAG20-TECHS-20160317/C18
C18: Using CSS margin and padding rules instead of spacer images for layout design | Techniques for...
css margin and padding