The popup menus for the DSSSilver theme were difficult to see over the background.  I modified my DSSSilver.css file as follows.  This creates a nice shadow effect around the popup making it easier to see that it is a popup menu.

/* Forum Main Menu (For navigation in forum and blog) Till END OF FILE*/
.ForumMenu_MenuContainer {
    border-left: #F1F1F1; 0px solid;
    border-right: #F1F1F1; 0px solid; 
    border-top: #F1F1F1; 0px solid;
    border-bottom: #F1F1F1; 0px solid;
    background-color: #F1F1F1;
}
.ForumMenu_MenuBar
{
 cursor: hand;
 color: #000099;
 background-color: #F1F1F1;
        height:10px;
}
.ForumMenu_MenuItem
{
 border-left: #ffffff 0px solid;
 border-right: #ffffff 0px solid;
 border-top: #ffffff 1px solid;
 border-bottom: #ffffff 1px solid;
 font-family: Tahoma, Arial, Helvetica;
 font-style: normal;
 font-weight: normal;
 text-decoration:none;
 cursor: hand;
 color: #000000;
 height: 18px;
}
.ForumMenu_MenuIcon {
    cursor: pointer;
    cursor: hand;
    background-color: #FFFFFF;
    border-left: #ffffff 1px solid;
    border-right: #ffffff 0px solid;
 border-top: #ffffff 1px solid;
 border-bottom: #ffffff 1px solid;
 width:16px;
 height:18px;
    text-align: center;
}

.ForumMenu_MenuArrow {
    border-right: #ffffff 1px solid;
    border-left: #ffffff 0px solid;
 border-top: #ffffff 1px solid;
 border-bottom: #ffffff 1px solid;
    font-family: webdings;
    font-size: 10px;
    cursor: pointer;
    cursor: hand;    
}

.ForumMenu_RootMenuArrow {
    border-right: #ffffff 1px solid;
    border-left: #ffffff 0px solid;
 border-top: #ffffff 1px solid;
 border-bottom: #ffffff 1px solid;
    font-family: webdings;
    font-size: 10px;
    cursor: pointer;
    cursor: hand;    
}

.ForumMenu_MenuItemSel
{
 border-color: #000099;
 background-color: #CCC;
 font-family: Tahoma, Arial, Helvetica;
 font-style: normal;
 font-weight: normal;
 text-decoration:none;
 height: 18px;
 cursor: hand;
 color: #000000;

}
.ForumMenu_SubMenu
{
 border-left: #cccccc 1px solid;
 border-right: #cccccc 1px solid;
 border-top: #cccccc 1px solid;
 border-bottom: #cccccc 1px solid;
 z-index: 1000;
 filter: progid:DXImageTransform.Microsoft.Shadow(color= 'DimGray' , Direction=135, Strength=3);
 cursor: hand;
 background-color: #ffffff;
}

.ForumMenu_MenuBreak {
 border-left: transparent 0px solid;
 border-bottom: white 1px solid;
 border-top: transparent 0px solid;
 border-right: transparent 0px solid;
 background-color: transparent;
 height: 0px;
}