Bootstrap格式转换代码

网址：http://www.w3cschool.cc/bootstrap/bootstrap-responsive-utilities.html

<div class="container" style="padding: 40px;">
   <div class="row visible-on">
      <div class="col-xs-6 col-sm-3" style="
         box-shadow: inset 1px -1px 1px #444, inset -1px 1px 1px #444;">
         <span class="hidden-xs">特别小型</span>
         <span class="visible-xs">✔ 在特别小型设备上可见</span>
      </div>
      <div class="col-xs-6 col-sm-3" style="
         box-shadow: inset 1px -1px 1px #444, inset -1px 1px 1px #444;">
         <span class="hidden-sm">小型</span>
         <span class="visible-sm">✔ 在小型设备上可见</span>
      </div>
      <div class="clearfix visible-xs"></div>
      <div class="col-xs-6 col-sm-3" style="
         box-shadow: inset 1px -1px 1px #444, inset -1px 1px 1px #444;">
         <span class="hidden-md">中型</span>
         <span class="visible-md">✔ 在中型设备上可见</span>
      </div>
      <div class="col-xs-6 col-sm-3" style="
         box-shadow: inset 1px -1px 1px #444, inset -1px 1px 1px #444;">
         <span class="hidden-lg">大型</span>
         <span class="visible-lg">✔ 在大型设备上可见</span>
      </div>
    </div>
</div>