my animation script does not work

i have wrote a script that should when i press the "W,A,S,D" keys my character walks forward,backwards an idles. but when i press the keys wasd my character moves but it dosent do the animation that ive created please can anyone help?

    var maxWalkSpeed = 10.0;
var maxTurnSpeed = 100.0;
function Update () {
    // Get the horizontal and vertical axis.
    // By default they are mapped to the arrow keys.
    // The value is in the range -1 to 1
    var walkSpeed = Input.GetAxis ("Vertical") * maxWalkSpeed;
    var turnSpeed = Input.GetAxis ("Horizontal") * maxTurnSpeed;
    // Move translation along the object's z-axis
    transform.Translate (0, 0, walkSpeed * Time.deltaTime);
    // Rotate around our y-axis
    transform.Rotate (0, turnSpeed * Time.deltaTime, 0);
}