如何在面板内删除asp：image的未知白色边框

Question

我有一个asp：图像控件的白色边框，我想删除它但找不到问题所在

这是我的html和css：

<asp:Panel runat="server" CssClass="nav" ID="nav">
     <asp:Image runat="server" ID="Logo" CssClass="logo" />
     <asp:LinkButton runat="server" ID="lb1" CssClass="navButtons">Home</asp:LinkButton>
     <asp:LinkButton runat="server" ID="LinkButton1" CssClass="navButtons">Restorant</asp:LinkButton>
     <asp:LinkButton runat="server" ID="LinkButton2" CssClass="navButtons">Rooms</asp:LinkButton>
     <asp:LinkButton runat="server" ID="LinkButton3" CssClass="navButtons">Spa</asp:LinkButton>       
     <asp:LinkButton runat="server" ID="LinkButton4" CssClass="navButtons">Contact</asp:LinkButton>
     <asp:LinkButton runat="server" ID="LinkButton5" CssClass="navButtons">Contact</asp:LinkButton>
     <asp:LinkButton runat="server" ID="LinkButton6" CssClass="navButtons">Contact</asp:LinkButton>
</asp:Panel>

ID =“Logo”的图像是白色边框，我需要删除此边框

图片和导航面板的CSS：

.logo {
    width:100%;
    height:150px;
    background-image:url(Background/logo.jpg);
    float:left;
    background-repeat:no-repeat;
    -moz-background-size: 100% 100%;
    -o-background-size: 100% 100%;
    -webkit-background-size: 100% 100%; 
    background-size: 100% 100%;
    position:relative;
    border:none;    
}

.nav {
    position:absolute;
    background-color:black;
    opacity:0.6;
    filter: alpha(opacity=60);
    height:550px;
    width:250px;
    z-index:3;
    max-height:550px;
    max-width:250px;
}