效果：

html：

    <h1 class="title-style">Css3 callouts</h1>
    <div class="wrap">
      <div class="box pointer--bottom">
        <p class="text--center">Pointer bottom</p>
      </div>
      <div class="box pointer--top">
        <p class="text--center"
 
>Pointer top</p>
      </div>
      <div class="box pointer--left">
        <p class="text--center">Pointer left</p>
      </div>
      <div class="box pointer--right">
        <p class="text--center">Pointer right</p>
      </div>
    </
 
div>
  </div>

CSS：

.wrap {
  padding-left: 7%;
}

.title-style {
  text-align: center;
  font-weight: 100;
  font-size: 3em;
  color: #346BB3;
}

.box {
  width: 32.40741%;
  float: left;
  margin-left: 0.46296%;
  margin-right: 0.46296%;
  position: relative;
  background
 
: #346BB3;
  color: #fff;
  padding: 1%;
  margin: 5%;
  white-space: nowrap;
  border-radius: 5px;
}

.box:after {
  content: "";
  position: absolute;
  height: 0;
  width: 0;
  border: solid transparent;
  pointer-events: none;
  border-width: 16px;
  border-color: #fff;
}

.pointer--bottom {
  animation: animimate-pointer--bottom 500ms ease-in-out;
  transform-origin: bottom center;
}

.pointer--bottom:after {
  margin-left: -16px;
  border-top-color: #346BB3;
  top: 100%;
  left: 50%;
}

.pointer--top {
  animation: animimate-pointer--top 500ms ease-in-out;
  transform-origin: top center;
}

.pointer--top:after {
  margin-left: -16px;
  border-bottom-color: #346BB3;
  top: -32px;
  left: 50%;
}

.pointer--left {
  animation: animate-pointer--left 500ms ease-in-out;
  transform-origin: left center;
}

.pointer--left:after {
  border-right-color: #346BB3;
  top: 25%;
  left: -32px;
}

.pointer--right {
  animation: animate-pointer--right 500ms ease-in-out;
  transform-origin: right center;
}

.pointer--right:after {
  border-left-color: #346BB3;
  top: 25%;
  right: -32px;
}

@keyframes animimate-pointer--bottom {
  0% {
    opacity: 0;
    transform: scale(0.1) rotate(30deg) translateY(50px) rotateX(90deg);
  }

  50% {
    transform: rotate(-10deg) rotateX(-2deg);
    opacity: 1;
  }

  70% {
    transform: rotate(3deg);
  }

  100% {
    transform: scale(1);
  }
}

@keyframes animimate-pointer--top {
  0% {
    transform: scale(0.1) rotate(-30deg) translateY(-50px) rotateX(-90deg);
    opacity: 0;
  }

  50% {
    transform: rotate(10deg) rotateX(2deg);
    opacity: 1;
  }

  70% {
    transform: rotate(-3deg);
  }

  100% {
    transform: scale(1);
  }
}

@keyframes animate-pointer--left {
  0% {
    transform: rotate(0deg) rotateX(-30deg);
    opacity: 0;
  }

  50% {
    transform: rotate(-10deg);
    opacity: 1;
  }

  70% {
    transform: rotate(10deg) rotateX(30deg);
  }

  100% {
    transform: rotate(0deg);
  }
}

@keyframes animate-pointer--right {
  0% {
    transform: rotate(0deg) rotateX(30deg);
    opacity: 0;
  }

  50% {
    transform: rotate(10deg);
    opacity: 1;
  }

  70% {
    transform: rotate(-10deg) rotateX(-30deg);
  }

  100% {
    transform: rotate(0deg);
  }
}

CSS3 之高級動畫（7）CSS3帶方向箭頭的標註框