CSS21/box.html#collapsing-margins"/>
  <style type="text/css">
   td { width: 3em; padding: 0; }

   .test { background: fuchsia; }
   .a { margin: 0; height: 1em; background: aqua; }
   .b { margin: 0; background: red; }
   .e { margin: 0; background: purple; height: 1em; float: left; width: 100%; }
   .c { margin: 0; background: red; }
   .d { margin: 0; background: red; }
   .f { margin: 0 0 1em 0; background: red; }

   .control { background: red; }
   .aqua { border-top: solid 1em aqua; }
   .fuchsia {