fazer dropdown menu aparecer

[Clauido José 3]

Bom dia galera,

 

Estou personalizando um navbar e tem dois dropdown que quero que seja de tamanhos diferentes e o posicionamento tambêm,  já consegui fazer ele sumir via css mais não consigo fazer ele aparecer  olha como esta meu código:

        <!-- Navegação -->
        <!--Inicio Nav-->
        <nav class="navbar navbar-default" role="navigation">
            <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>
                </div>
                <div class="collapse navbar-collapse" id="myNavbar">
                    <ul>
                        <li class="nav-item"><a href="#"><span class="glyphicon glyphicon-home" style="padding: 0px 5px"></span>Home</a></li>
                        <li class="nav-item"><a href="#"><span class="glyphicon glyphicon-info-sign" style="padding: 0px 5px"></span>A Empresa</a></li>

                        <li id="persianas">
                            <a href="#">
                                <span class="glyphicon glyphicon glyphicon-th" 
                                            style="padding: 0px 5px"></span>
                                Persianas <span class="caret"></span></a>
                            <ul>
                                <asp:DataList ID="itemPersianas" RepeatColumns="1" runat="server">
                                    <itemtemplate>
                                        <li><span style="padding-left:15px;"></span><a href="produtos.aspx?ProdutosId=<%# Eval("MenuId")%>">
                                            <%#  Eval("Titulo") %>
                                        </a></li>
                                    </itemtemplate>
                                </asp:DataList>
                            </ul>
                        </li>
                        <li>
                            <a href="#"><span class="glyphicon glyphicon-th-large" style="padding: 0px 5px"></span>
                                Cortinas <span class="caret"></span></a>
                            <ul id="cortinas">
                                <asp:DataList ID="itemCortinas" RepeatColumns="1" runat="server">
                                    <itemtemplate>
                                        <li><span style="padding-left:15px;"></span><a href="produtos.aspx?ProdutosId=<%# Eval("MenuId")%>">
                                            <%#  Eval("Titulo") %>
                                        </a></li>
                                    </itemtemplate>
                                </asp:DataList>
                            </ul>
                        </li>
                        <li class="nav-item"><a href="#"><span class="glyphicon glyphicon-globe" style="padding: 0px 5px"></span>Parceiros</a></li>
                        <li class="nav-item"><a href="#"><span class="glyphicon glyphicon-envelope" style="padding: 0px 5px"></span>Contato</a></li>
                    </ul>
                    <form class="navbar-form  navbar-right" runat="server" role="search" action="#" method="get" id="BuscaForm">
                        <div class="input-group" id="pesquisa">
                            <asp:TextBox ID="BuscaTextBox" runat="server" class="form-control" placeholder="Pesquisar produtos" name="BuscaTextBox" style="padding:6px 6px;"></asp:TextBox>
                            <div class="input-group-btn">
                                <button class="btn btn-default" id="PesquisaButton" type="submit"><i class="glyphicon glyphicon-search"></i></button>
                            </div>
                        </div>
                    </form>
                </div>
            </div>
        </nav>
        <!-- Fim Navegação -->

/* navbar
/* barra de menu principal */
.navbar-default {
	background: -moz-linear-gradient(top,  #CCC 80%, #fefefd 100%); /* FF3.6+ */
	background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#f2f2f1), color-stop(100%,#fefefd)); /* Chrome,Safari4+ */
	background: -webkit-linear-gradient(top,  #CCC 80%,#fefefd 100%); /* Chrome10+,Safari5.1+ */
	background: -o-linear-gradient(top,  #CCC 80%,#fefefd 100%); /* Opera 11.10+ */
	background: linear-gradient(to bottom,  #CCC 80%,#fefefd 100%); /* W3C */
    border-color: #E7E7E7;
    height:55px;
    font-size:18px
}
.navbar-default a{
    color: #fff;
    padding:10px;
    display:block;
    text-decoration:none;
    text-align:center;
    background-color: #ccc;
    height:45px;
}
.navbar-default a:hover{
    background-color:#FFF;
    color:#000
}
 .navbar-default ul{
     list-style-type:none;
     position:relative;
 }  
 .navbar-default ul li{
     width:150px;
     float:left;
 }
 /*primeiro dropdown*/
 .navbar-default #persiana:hover ul {
     visibility:visible;
 }
 .navbar-default #persianas li{
     width:250px;
     font-size:16px;
     margin:-10px -50px;
    border-radius: 10px;
    box-shadow: 5px 5px black;
    visibility:hidden;
 }
 .navbar-default #persiana a:hover ul {
     visibility:visible;
 }
 /*segundo dropdown*/
 .navbar-default #cortinas{
     position:absolute;
     visibility:hidden
 }
 /*Fim navbar*/