ASP:Menu is not properly working in IIS

Question

I have an asp menu which is working great in debug mode but when website is published it does not work in IIS. Below is working fine in Visual Studio 2010 Debug mode:

But child menu not appear when hover on this menu in IIS:

Here is html code & css.

<div id="menu">
           <asp:Menu id="Menu1" Orientation="Horizontal" Runat="server" 
                OnMenuItemClick="Menu1_MenuItemClick">
           </asp:Menu>
</div>

#menu {  }
#menu a 
{
    display: block;
    float: left;
    margin: 0 10px 0 0;
    border-bottom: solid 1px #B79845 !important;
    padding: 8px 0px 0px 0px;
    text-decoration: none;
    text-align: center;
    font-family: David;
    font-size: 14px;
    color: #000000;
    height: 18px;
    width: 183px;
}

#menu a:hover {
    margin: 0 3px 0 0;
    background-color: #B79845;
    color: #303822;
    font-weight: 900;
    height: 18px;
    width: 183px;
}