twitter bootstrap折叠在单击时删除边框

Question

您好我目前有这个问题，当我点击折叠按钮显示我的导航栏链接时，我的透明导航栏突然出现这个黑色边框。即使我将边框颜色设置为透明，我也不明白为什么会出现这条线。

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我的HTML代码：

nav class="navbar navbar-inverse" style="background-color:transparent; height:94px; padding:none; border-color:transparent;">
  <div class="container-fluid">
    <div class="navbar-header">
      <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#myNavbar">
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>                        
      </button>
      <a class="navbar-brand" style=""><%=image_tag "elem_logo-white.png", :style => "width: 95%;"%> </a>
    </div>
    <div class="collapse navbar-collapse" id="myNavbar">
      <ul class="nav navbar-nav navbar-right">
                  <% if user_signed_in? %>`
        <li role="presentation" class="dropdown" style=" margin:20px 60px 0px 20px;">
          <a class="dropdown-toggle" data-toggle="dropdown" href="#" role="button" aria-haspopup="true" aria-expanded="false" style="font-size:19px;margin:none; color:white;">
            <%= current_user %> <span class="caret"></span>
          </a>

          <ul class="dropdown-menu">

            <% if current_user.try(:admin?) %>
            <li>
              <p class="" href="#login" data-toggle="modal">
              <center>

              <%= link_to "DASHBOARD",admin_dashboard_path, :style=>"font-size:14px; margin-left:12px;" %>

              </center></p>
            </li>
            <% else %>
            <li>
                <p class="" href="#login" data-toggle="modal"><center><%= link_to "PROFILE", hound_user_path(current_user.id), :style=>"font-size:14px; margin-left:12px;" %></center></p>
            </li>
            <%end%>


            <li><hr></li>
            <li>
              <p class="" href="#login" data-toggle="modal"><center><%= link_to "SIGN OUT", destroy_user_session_path, :style=>"font-size:14px; margin-left:12px;" %></center></p>
            </li>
          </ul>
        </li>
        <%else%>
        <li style=" margin:20px 10px 0px 20px;"><a style="font-size:22px;margin:none; color:white; outline:0;" href="#login" data-toggle="modal"><b>LOG IN</b></a></li>

         <li style=" margin:20px 50px 0px 10px;"><a style="font-size:22px;margin:none; color:white;" href="#signup" data-toggle="modal"><button style="height: 40px; width:150px; border-radius: 20px; border: solid 1px; background-color: transparent; margin-top:-10px; outline:0;"><b>SIGN UP</b></button></a></li>
        <% end %>
      </ul>
    </div>
  </div>
</nav>

任何人都可以帮助我吗？谢谢！