纯css制作三角箭头提示框

html:
<div class="speech-bubble speech-bubble-top">
  箭头在顶部
</div>
<br/>
<div class="speech-bubble speech-bubble-bottom">
  箭头在底部
</div>
<br/>
<div class="speech-bubble speech-bubble-left">
  箭头在左侧
</div>
<br/>
<div class="speech-bubble speech-bubble-right">
  箭头在右侧
</div>

css：
.speech-bubble {
  position: relative;
  background-color: #292929;
  width: 200px;
  height: 150px;
  line-height: 150px;
  /* 垂直居中 */
  color: white;
  text-align: center;
  border-radius: 10px;
  font-family: sans-serif;
}
.speech-bubble:after {
  content: '';
  position: absolute;
  width: 0;
  height: 0;
  border: 15px solid;
}
/* 箭头的位置 */
.speech-bubble-top:after {
  border-bottom-color: #292929;
  left: 50%;
  bottom: 100%;
  margin-left: -15px;
}
.speech-bubble-right:after {
  border-left-color: #292929;
  left: 100%;
  top: 50%;
  margin-top: -15px;
}
.speech-bubble-bottom:after {
  border-top-color: #292929;
  top: 100%;
  left: 50%;
  margin-left: -15px;
}
.speech-bubble-left:after {
  border-right-color: #292929;
  top: 50%;
  right: 100%;
  margin-top: -15px;
}


效果参见：http://jscssshare.com/#/sample/oaDqPMUk