<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"> <html lang="en"> <head> <title>Margin Collapsing: float positioning</title> <style type="text/css"> table, td { padding: 0; border-spacing: 0; } .comparator { border-spacing: 1em; } .test, .control { border: solid; background: lime; } .test .top { display: block; margin: 0; height: 1em; width: 8em; background: yellow; } .test .container { display: block; margin: 1em 0 0 0; width: 8em; background: red; } .test .float { float: left; margin: 0; height: 1em; width: 8em; background: yellow; } .test .block { display: block; margin: 2em 0 0 0; height: 1em; background: red; } .control .lime { border-top: 2em solid lime; width: 8em; } .control .yellow { border-top: 1em solid yellow; } </style> </head> <body> <p>The following two squares should be identical.</p> <table class="comparator"> <tr> <td class="test"> <div class="top"> </div> <div class="container"> <div class="float"> </div> <div class="block"> </div> </div> </td> <td class="control"> <div class="yellow"> </div> <div class="lime"> </div> <div class="yellow"> </div> </td> </tr> </table> </body> </html>