Udenineret variabel fejl

Fejlen:

Microsoft VBScript runtime error '800a01f4'

Variable is undefined: 'mode'

/skp/cv.asp, line 13

KODEN:
<%@LANGUAGE="VBSCRIPT" CODEPAGE="CP_ACP"%>
<% option explicit %>
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<!--#include file="style.css"-->
<!--#include file="header.inc"-->
<!--#include file="elevmenu.inc"-->
<body>
<%
mode = Request.QueryString("mode") 'linje 13
if mode = "" then mode = "start"
select case mode %>
<%
case "start"
%>

<%
Dim dbData, rsData, SQL, Path
Set dbData = Server.CreateObject("ADODB.Connection")
Path = "DBQ=" & server.mappath("skp.mdb")
dbData.Open "DRIVER={Microsoft Access Driver (*.mdb)};"&Path
Set rsData = Server.CreateObject("ADODB.Recordset")
SQL = "SELECT * FROM tblElev WHERE id=" & Session("idUser")
rsData.Open SQL, dbData

'//Henter brugeren data med Sessionen idUser
%>