Javascript Validation

<script id="script2" type="text/javascript">

function Propsectvalidate() {

               //Start---Validation for checkbox list

        if (document.getElementById("<%=chklProductType.ClientID%>") != null) {
          
        var isChecked = 0;
        var list = document.getElementById('<%= chklProductType.ClientID %>');
        var chkList = list.getElementsByTagName("input");

        for (var i = 0; i < chkList.length; i++) {
            if (chkList[i].checked) {
                isChecked = 1;
              
            }
        }
          if(isChecked==0)
            {
            alert("Please Check Product Type");
            document.getElementById("<%=chklProductType.ClientID%>").focus();
            return false;
            }
    }

    //End--Validation for checkbox list---

        if (document.getElementById("<%=txtNameofBusiness.ClientID%>").value == "") {
            alert("Prospect Name can not be blank");
            document.getElementById("<%=txtNameofBusiness.ClientID%>").focus();
            return false;
        }

//Start---Validation for dropdown list

               if (document.getElementById("<%=ddlState.ClientID %>").value == 0) {
            alert("Please select the State");
            document.getElementById("<%=ddlState.ClientID %>").focus();
            return false;
        }

//End----Validation for dropdown list
            

    }
    </script>

<asp:ImageButton ID="btnSubmit" runat="server" ImageUrl="~/images/Buttons/save.png" OnClick="btnSubmit_Click"  CausesValidation="False" Visible="false" OnClientClick=" return Propsectvalidate()" />