im writing the code in microsoft visual st.. and it workes fine exept it dose not seam to understand this ("speed", 3f);

Could you provide the error text?

Parameter 'speed' does not exist. UnityEngine.Animator:SetFloat(String, Single) Movingfrog:FixedUpdate() (at Assets/Scripts/Movingfrog.cs:30)

That sounds like your playerAnimator doesn't have a speed variable. Make sure you didn't capitalize the variable name differently in the animator, i.e. Speed, SPEED

this is all of the code... i cant find the mistake: public class Movingfrog : MonoBehaviour {

private Animator playerAnimator;
private float moveHorizontal;
private float moveVertical;
private Vector3 movement;

// Use this for initialization
void Start () {
    playerAnimator = GetComponent<Animator> ();
}

// Update is called once per frame
void Update () {
    moveHorizontal = Input.GetAxisRaw ("Horizontal");
    moveVertical = Input.GetAxisRaw ("Vertical");

    movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
}

private void FixedUpdate()
{
   if (movement != Vector3.zero) {
        playerAnimator.SetFloat ("speed", 3f);
   } else {
        playerAnimator.SetFloat ("speed", 0f);
   }
} 

}

Judging by the error message, the script isn't the problem. The problem will be inside the Animator component. You have to look at the Animator and make sure your variable is correctly named.

thank you