浏览器版本过低

http://study.163.com/common/errors/notSupported.htm

<div class="wb f-cb">

 <a href="http://www.google.cn/intl/zh-CN/chrome/browser/" class="g f-hide" target="_blank">谷歌浏览器</a> 

<a href="http://firefox.com.cn/download/" class="f f-hide" target="_blank">Firefox</a>

 <a href="http://windows.microsoft.com/zh-CN/internet-explorer/downloads/ie" class="ie f-hide" target="_blank">Internet Explorer 8+</a>

 </div>