<a href="javascript:void(0);">
キャプションが入ります。
</a>
body{
  font-size: 14px;
  color: #333;
}
a{
  color: #333;
  text-decoration: none;
  position:relative;
}
a:after{
  content: "";
  position: absolute;
  left: 0;
  bottom: -6px;
  width: 0;
  height: 2px;
  background-color: #337ab7;
  transition-duration: 3s;
  transition-delay:2s;
}
a:hover:after{
  width: 100%;
}

External CSS

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External JavaScript

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