My Js Script is not working

There's nothing as a dumb question.

Try this out:

 function OnCollisionEnter () {
     Application.LoadLevel(1);
 }

Remove the Update () and only do the above. If the object is set to trigger then use OnTriggerEnter instead. Remember that they are separate functions and they can't run inside Update.

If you only want a specific object by tag trigger the level loading then add:

 function OnCollisionEnter (collision : Collision) {
     if (collision.collider.tag!="The Tag") return;
     Application.LoadLevel(1);
 }

If it is a trigger then use this instead:

 function OnTriggerEnter (other: Collider) {
     if (!other.CompareTag("The Tag")) return;
     Application.LoadLevel(1);
 }