<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"> <html lang="en"> <head> <title>Margin Collapsing: top margins</title> <style type="text/css"> .test { background: aqua; margin: 0; width: 6em; border: solid; } .test .a { height: 1em; background: fuchsia; margin: 0; } .test .b { background: red; margin: 0; } .test .c { float: left; height: 1em; width: 3em; background: orange; margin: 0; } .test .d { height: 1em; background: yellow; margin: 1em 0 0 0; } .control { width: 6em; border: solid; } .control .a { border-top: fuchsia 1em solid; } .control .b { border-top: aqua 1em solid; } .control .c { border-left: orange 3em solid; border-right: yellow 3em solid; height: 1em; } </style> </head> <body> <p>The two boxes below should look identical.</p> <table> <tr> <td> <div class="test"> <div class="a"></div> <div class="b"> <div class="c"></div> <div class="d"></div> </div> </div> </td> <td> <div class="control"> <div class="a"></div> <div class="b"></div> <div class="c"></div> </div> </td> </tr> </table> </body> </html>