anchor.diff: -<header class="navbar navbar-inverse navbar-static-top mech-nav">
  +<nav class="navbar navbar-inverse navbar-static-top mech-nav">
     <div class="container">
       <div class="navbar-header">
         <button class="navbar-toggle" type="button">
  
positive.code:           <li><%= link_to "登录", signin_path %></li>
          <% end %>
        </ul>
      </nav>
    </div>
  </header>
negative.code:       </button>
        <a href="/" class="navbar-brand"><%=image_tag("mech-logo-s.png",:class => "mech-nav-logo")%></a>
      </div>
      <div class="navbar-collapse collapse">
        <ul class="nav navbar-nav">
          <li>
            <a href="/">首页</a>
  