什么是标签？如何创建标签？
标签是放在文本后面的提示信息，一般用 <span>外加 .label .label-default 创建
<h1>一号文本 <span class = "label label-default">标签</span></h1>
<h2>二号文本 <span class =" label label-default">标签</span></h2>
<h3>三号文本 <span class = "label label-default">标签</span></h3>
<h4>四号文本 <span class = "label label-default">标签</span></h4>
01.PNG
能够改变标签的外观样式吗？
.label-default, .label-primary, .label-success, .label-info, .label-warning, .label-danger 这几个类可以改变标签的外观样式
<span class = "label label-default">Default Label</span>
<span class = "label label-primary">Primary Label</span>
<span class = "label label-success">Success Label</span>
<span class = "label label-info">Info Label</span>
<span class = "label label-warning">Warning Label</span>
<span class = "label label-danger">Danger Label</span>
02.PNG
