/20px serif;
  margin: 1em 0em;  
  }
  
  div#grand-parent
  {
  width: 400px;
  }

  div#parent
  {
  background-color: lime;
  border: white solid 3px; /* Such border prevents margin collapsing among vertical margins */
  margin: 25%; /* 25% of 400px == 100px; */
  width: 200px;
  }

  div#child
  {
  margin: inherit; 
  /* computes to 25% which is then applied on #child's containing block width: 25% of 200px == 50px */
  }

  div#abs-pos-overlapping-lime
  {
  left: 161px;
  position: absolute;
  top: 2