Some properties can have values that require refinement to compute their value
Refinement occurs after inheritance
Examples of refinement:
shortcuts such as font which map to multiple properties such as font-size, font-weight, etc.
cases where multiple properties can affect similar traits such as padding-left and padding-start or space-before and margin-top
values (e.g., margins) that can be specified in terms of percentage of the column width need to be resolved to a distance