NOTE: there are some examples with notes in the-web-developer-bootcamp repo --- and more examples in build-responsive-real-world-websites-with-html5-css3 repo

NOTE: images are screenshots from Build Responsive Real World Websites with HTML5 and CSS3 by Jonas Schmedtmann

  • Cascading Stye Sheets
  • defines exactly how the HTML should look
  • can be written in 3 places:
    • inside an HTML tag (in index.html)
      <p style="font-size: 120%"></p>
    • inside an HTML document (in index.html)
          p {
              font-size: 120%
    • in an external file (in style.css)
      p {
          font-size: 120%;


  • css is written in rules
    • each rule contains a selector and a declaration block
  • selector {
        /*declaration block*/
  • child elements inherit styles from their parent elements (e.g. an h1 will inherit from body) unless we override their styles
    • the most specific selector will be the one displayed
  • the * selector affects everything


  • the RGB model --- each color can range from 0 (hex 0) to 255 (hex ff)
    • colors written using hex notation look like #RRGGBB
    • colors can be transparent
      • don't use hex notation --- use rgba(R, G, B, transparency percent (0 is completely transparency, 1 is opaque)

RGB Color Model

Classes and IDs

  • classes can be used on as many elements as we want
  • ids can only be used once
    • using ids is considered bad practice because they can only be used once --- usually use classes for all styling even if there is only one element with the class --- this allows for easier changes in the future

The Box Model

The CSS Box Model

  • with box-sizing: border-box, the height and width of the entire box can be defined rather than just for the content
    • there are block, inline, and inline-block elements
      • block Block Elements
        • use the full width of the browser
      • inline Inline Elements
        • can set height and/or width
      • inline-block
        • doesn't have a line-break like a regular inline element, but can have margin and padding like a block element

Relative vs. Absolute Positioning

  • relative --- position determined by other elements in the page
  • absolute --- can be positioned anywhere inside their parent element
    • the parent element's position must be set to relative

Copyright © 2022