What is wrong in this code?

public void LoadLevel(string name){
Debug.Log ("New Level load: " + name);
Application.LoadLevel (name);
FadeOut(audioSource: 3f);

	public void QuitRequest(){
		Debug.Log ("Quit requested");
		Application.Quit ();
		public static IEnumerator FadeOut (AudioSource audioSource, float FadeTime) {
			float startVolume = audioSource.volume;
			while (audioSource.volume > 0) {
				audioSource.volume -= startVolume * Time.deltaTime / FadeTime;
				yield return null;
			audioSource.Stop ();
			audioSource.volume = startVolume;

What is wrong in this line

FadeOut(audioSource: 3f);

Thanks a lot.

FadeOut(audioSource, 3f);

Positive7 showed you the compiler error, but you have more problems there. Read more about coroutines here, read carefully how you start a coroutine (i.e. using the StartCoroutine method).

Also, you showed a portion of a script, but I’ll assume the game object that has that script attached is destroyed when loading a new scene. If that’s the case your coroutine won’t work, read here how to keep an object in the hierarchy while loading a new scene.