The user agent performs four steps to calculate a property's actual (final) value:

1. First, the specified value is determined based on the result of cascading, inheritance, or using the initial value.
2. Next, the computed value is calculated according to the specification (for example, a span with position: absolute will have its computed display changed to block).
3. Then, layout is calculated, resulting in the used value.
4. Finally, the used value is transformed according to the limitations of the local environment, resulting in the actual value.

• CSS key concepts:
  • CSS syntax
  • At-rules
  • Comments
  • Specificity
  • Inheritance
  • Box model
  • Layout modes
  • Visual formatting models
  • Margin collapsing
  • Values
    • Initial values
    • Computed values
    • Used values
  • Value definition syntax
  • Shorthand properties
  • Replaced elements