Download a static site with all the prebuilt html and css and view it in the browser. Next, think of some major or potentially difficult change you'd like to make to it with regard to layout, size, font, etc. With the help of the browser's developer tools, you'll be able to identify the styles that need to change for the elements involved. You'll learn something from the existing css, and you'll learn a lot by trying to mess with it. Today, most people use a css framework like Bootstrap or Materialize for accomplishing the flexibility for different displays you're looking for. Read the API documentation for one of these frameworks and look through the examples. Alternatively, there's a nice React ui framework from Microsoft over at https://developer.microsoft.com/en-us/fabric#/styles/web It uses the same responsive grid layout principles that have become de facto standard. If you want to get into React, you're going to need to know some Javascript because React uses Typescript which transpiles to JS and you'll need to understand possibly both languages. Additionally, you'll probably see some use of Redux.