hello,

in Visual Studio, i opened a css file of DNN and it says that there is a wrong with "filter" keywork.

.main_dnnmenu_submenu {
    background-color: #cad5ea; 
    z-index: 1000;
    cursor: pointer;
    cursor: hand;
    filter:progid:DXImageTransform.Microsoft.Shadow(color='#696969', Direction=135, Strength=3);
    padding: 1px 1px 1px 1px;   /*explicitly set padding for sub-menus */
}

if dont know much about css but if there's really an error, it would be better if it is corrected.

Yes, it's IE specific. Will be removed if the new webcontrols are released I think.