1.bootrap的悬停显示

   只需要引入bootstrap的js,css即可。关键代码

$('a').tooltip({title: "我是一个提示框，我在顶部出现",placement: "top"});

 优点：好看，适用于单个。

2.jqury的悬停显示

   只需要引入jquery.js，小demo如下

<!doctype html>
<html>
<head>
  <meta charset="utf-8">
  <title>jQuery UI Tooltip - Default functionality</title>
  <link rel="stylesheet" href="//code.jquery.com/ui/1.11.4/themes/smoothness/jquery-ui.css">
  <script src="//code.jquery.com/jquery-1.10.2.js"></script>
  <script src="//code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
  <script>
  $(function() {
    $( document ).tooltip();
  });
  </script>
  
</head>
<body>
 
<p><a href="#" title="That's what this widget is">Tooltips</a> can be attached to any element. When you hover
the element with your mouse, the title attribute is displayed in a little box next to the element, just like a native tooltip.</p>
<p>But as it's not a native tooltip, it can be styled. Any themes built with
<a href="http://jqueryui.com/themeroller/" title="ThemeRoller: jQuery UI's theme builder application">ThemeRoller</a>
will also style tooltips accordingly.</p>
<p>Tooltips are also useful for form elements, to show some additional information in the context of each field.</p>
	<p><label for="age">Your age:</label><input id="age" title="We ask for your age only for statistical purposes."></p>
<p>Hover the field to see the tooltip.</p>
 
 
</body>
</html>

关键代码如下： 

$(function() {
    $( document ).tooltip();
  });


 意思是在加个title，就能悬停显示title里面的内容 

<input id="age" title="We ask for your age only for statistical purposes.">