引导工具提示(3.3.6)显示灰色框

<!-- Bootstrap CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">

<!-- jQuery -->
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>

<!-- Bootstrap JS -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>

$(document).ready(function(){
    $('[data-toggle="tooltip"]').tooltip();   
});

<button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="top" title="Tooltip on top" data-trigger="hover">
  Tooltip on top
</button>