Bootstrap 教程尝试一下

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<!DOCTYPE html>
<html>
  <head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="http://apps.bdimg.com/libs/bootstrap/3.3.0/css/bootstrap.min.css">
  </head>

<body>
    <div class="container">
      <h2>Chevron-down Glyph</h2>
      <p>Chevron-down icon: <span class="glyphicon glyphicon-chevron-down"></span></p>    
      <p>Chevron-down icon as a link:
        <a href="#">
          <span class="glyphicon glyphicon-chevron-down"></span>
        </a>
      </p>
      <p>Chevron-down icon on a button:
        <button type="button" class="btn btn-default btn-sm">
          <span class="glyphicon glyphicon-chevron-down"></span> Chevron-down
        </button>
      </p>
      <p>Chevron-down icon on a styled link button:
        <a href="#" class="btn btn-info btn-lg">
          <span class="glyphicon glyphicon-chevron-down"></span> Chevron-down
        </a>
      </p> 
    </div>

</html>