Chage level Whith time

Hello can some one help me, I am devloping a game in which you have to visit diferent places in a ‘‘X’’ amount of time I am using this code but I don’t know why it dosen work…

    function Start(){

yield WaitForSeconds(30);

Application.LoadLevel(1);

yield return new WaitForSeconds(30);
        Application.LoadLevel(2);

}

You should call a coroutine in which you will yield the processing of this script for the rest of the processing of your code.
try doing the following:

function Start()
{
    StartCoroutine("TimedLeveling");
}

function TimedLeveling()
{
    yield WaitForSeconds(30);
    Application.LoadLevel(1);

    yield WaitForSeconds(30);
    Application.LoadLevel(2);
}