<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"> <html lang="en"> <head> <title>Margin Collapsing: negative margins (easy)</title> <style type="text/css"> .container { background: red; height: auto; border-top: 1em lime solid; border-bottom: 1em lime solid; } .red { border-top: 1em solid red; } .lime { border-top: 1em solid lime; margin-top: -1em; } </style> </head> <body> <p>There should be no red below.</p> <div class="container"> <div class="red"></div> <div class="lime"></div> </div> </body> </html>