后台登陆验证

<%
dim username
dim password
 username=request.form("myuser")
 password=request.form("mypassword")
 set rs=server.createobject("adodb.recordset")
 sql="select * from users where u_user='"&username&"'"
 rs.open sql,conn,1,1
 if rs.eof then
  response.write "<script>alert('登录失败');history.back();</script>"
  response.end
  else
    if rs("u_password")<>"password" then
      response.write "<script>alert('登录失败');history.back();</script>"
      response.end     
     end if      
     session("admin")="username"
response.write"<script>alert('登录成功');location.href='index.asp'</script>"
  end if
%>


请问以上的代码哪里出错了吗? 为什么每次运行的时候都是弹出"登录失败" .知道的高手请指点我一下,谢谢了.