/* http://terkel.jp/archives/2009/12/css-only-speech-bubbles/ */

.bubble {
  float: left; /* または position: absolute; */
  border-left: 10px solid black;
  border-bottom: 10px solid transparent;
  -border-bottom-color: white; /* for IE6 */
}

.bubble .body {
  float: left; /* または width を明示 */
  margin-left: -20px;
  background: black;
  color: white;
  -position: relative; /* for IE6 */
}