<!DOCTYPE html> <html> <head> <style type="text/css"> #parent { height: 90px; background-color: blue; margin-bottom: 20px; } #child { height: 100px; background-color: green; margin-bottom: 20px; } #separator { height: 20px; background-color: green; } </style> </head> <body> <div id="parent"> <div id="child"></div> </div> <div id="separator"></div> </body> </html>