网页中添加悬浮窗

在网页中添加悬浮窗，自适应手机电脑平板，码如下：

<div id="kefu2">
<div class="cs_qcode" align="center">
<table >
  <tr>
    <th>微信扫一扫关注我</th>
  </tr>
  <tr>
  	<th>可用微信公众号搜索网课答案</th>
  </tr>
</table>
<picture>	
</picture>
<!--<img src="image/wechat.jpg" title="用手机微信扫一扫" width="50%" height="50%"/>-->
<picture>
<source srcset="image/wechat50.jpg" media="(max-width: 1800px)"> 
<source srcset="image/wechat150.jpg" media="(max-width: 1600px)"> 
<img srcset="image/wechat250.jpg" alt="pic">        
</picture>
</div>
</div>