WWW - Url change in coroutine is not working?

I use this WWW script: http://docs.unity3d.com/ScriptReference/WWW.html

It's working. But when I change the code to this:

Code (CSharp):

1.     using UnityEngine;
2.     using System.Collections;
3.    
4.     public class ExampleClass : MonoBehaviour {
5.         public string url = "http://images.earthcam.com/ec_metros/ourcams/fridays.jpg";
6.                
7.     void Start () {
8.  
9.         StartCoroutine (Co ());
10.        
11.     }
12.  
13.         IEnumerator Co() {
14.  
15.             // *** THIS IS THE NEW LINE ***
16.             url = "http://NEW URL";
17.                
18.             WWW www = new WWW(url);
19.             yield return www;
20.                
21.             Renderer renderer = GetComponent<Renderer>();
22.             renderer.material.mainTexture = www.texture;
23.         }
24.     }

It's not working. Why?

I printed the new URL in the console and tested it. The new url works.

So, the new url change in the coroutine is not working.

 

Your example works fine for me.
What do you mean by "not working". What happens?
Did you maybe put this code in a script named something other than "ExampleClass" ?