Final answer:
In CSS, the distance between two vertically aligned elements is the maximum of their two margins, not the sum or average.
Step-by-step explanation:
In CSS, when two elements are vertically aligned, the distance between the two elements will be the maximum of the two margins. If one element has a margin-bottom of 20px and the adjacent element has a margin-top of 30px, the space between the elements will be 30px, not 50px (the sum) or 25px (the average). This is due to the margin collapsing behavior in CSS.