<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"> <html lang="en"> <head> <title>Margin Collapsing: top margins</title> <style type="text/css"> .a { margin: 0; background: red; } .b { margin: 2em 0 0 0; background: red; } .c { margin: 0; background: red; } .d { margin: 1em 0 0 0; background: green; color: white; } </style> </head> <body> <p>There should be no red below.</p> <div class="a"> <div class="b"> <div class="c"> <div class="d"> This line should be green. </div> </div> </div> </div> </body> </html>