how to validate dropdownlist using javascript in asp.net

How to validate dropdownlist for must select an item leaving first item in asp.net through javascript.

function Dropdown_Validation(fieldid, msgid) {

    var empty = document.getElementById(fieldid).value;

    if (empty == "--Select--") {

        document.getElementById(msgid).innerHTML = "Please Select An Item";

        //document.getElementById(error_icon_star).innerHTML='<img src="WebResource.gif" height="15px" style="width:15px;"/>';

        return false;

    }

    document.getElementById(msgid).innerHTML = "&nbsp;";

    //document.getElementById(error_icon_star).innerHTML='<b style="color:Red">*</b>';

    return true;

}