<hr>标签失效问题
<div class="jumbotron">
<h1>Hello, world!</h1>
<hr>
<p>This is a template for a simple marketing or informational website. It includes a large callout called a jumbotron and three supporting pieces of content. Use it as a starting point to create something more unique.</p>
<hr>zai bootstrap中是不是不起作用??
