Input string was not in the correct format

Hi guys anybody know why im getting this error?

FormatException: Input string was not in the correct format System.Int32.Parse (System.String s) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System/Int32.cs:629) InternetCalls+c__Iterator2.MoveNext () (at Assets/Scripts/Level/InternetCalls.cs:85)

This is my script but i dont think that the string is in wrong format.

 public class InternetCalls : MonoBehaviour {
 
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 
     public void DoLogin(string User,string Pass)
     {
         WWWForm www = new WWWForm ();
         www.AddField ("user", User);
         www.AddField ("password", Pass);
 
         WWW w = new WWW ("http://reactivestudios.comuv.com/login.php", www);
         StartCoroutine (Login(w, User));
         GetXp (User);
     }
 
     public void DoRegister(string User,string Pass, string Name)
     {
         WWWForm www = new WWWForm ();
         www.AddField ("user", User);
         www.AddField ("password", Pass);
         www.AddField ("name", Name);
         
         WWW w = new WWW ("http://reactivestudios.comuv.com/register.php", www);
         StartCoroutine (Reg(w));
     }
 
     IEnumerator Reg (WWW w)
     {
         yield return w;
         if(w.error == null)
             {
                 //PlayerPrefs.SetString("name", User);
             Debug.Log ("Working");
             Debug.Log (w.text.ToString());
             }
     }
 
     IEnumerator Login (WWW w, string User)
     {
         yield return w;
         if(w.error == null)
         {
             if(w.text == "login-SUCCESS")
             {
                 PlayerPrefs.SetString("name",User);
                 Debug.Log ("Working");
                 Application.LoadLevel(1);
             }
         }
         else
         {
             Debug.Log ("Error:" + w.error.ToString());
         }
     }
 
     public void GetXp(string User)
     {
         WWWForm www = new WWWForm ();
         www.AddField ("user", User);
         WWW w = new WWW ("www.reactivestudios.comuv.com/Exp.php",www);
         StartCoroutine (Xp (w));
         Debug.Log ("Got Exp");
     }
     IEnumerator Xp(WWW w)
     {
         yield return w;
         if(w.error == null)
         {
             //PlayerPrefs.SetString("name", User);
             Debug.Log ("Getting Xp for Stats");
             Debug.Log (w.text);
             Debug.Log ("Working Stats");
             PlayerPrefs.SetInt("xp",int.Parse(w.text));
             Debug.Log ("Get xp Worked Stats");
         }
         else
         {
             Debug.Log ("Error: " + w.error.ToString());
     }
     }
 }