https://developers.google.com/web/tools/chrome-devtools/javascript/

HTML layout components and examples: https://getbootstrap.com/docs/4.0/examples/

https://forums.3dcart.com/forum/shopping-cart-software/store-design/74864-hide-show-content-on-mobile-desktop

3dCart https://grow.3dcart.com/hubfs/ebooks/Beginners%20Guide%20to%20Email%20Marketing.pdf?t=1516810076011