Conformation Box for Delete when Button click

<script type="text/javascript">
//conformation box for Delete
    function DeleteItem() {
        if (confirm("Are you sure you want to delete ...?")) {
            return true;
        }
        return false;
    }
</script>

// Link Button
 <asp:LinkButton ID="lkbtnDelete" runat="server" onclientclick="javascript:return DeleteItem();">Delete</asp:LinkButton>

or
// Button
<asp:Button ID="btnSave" runat="server" Text="Save"  onclientclick="javascript:return DeleteItem();" onclick="btnSave_Click" />