Need help with C# script

Hello, I have the problem that I can be with my people purely Login everyone and not just the people who stand in my mysql database. Please help where is my mistake.
this is my code:

using UnityEngine;
using System.Collections;

public class _Login : MonoBehaviour {

    private string UserID = "";
    private string Password = "";
    private string LoginURL = "http://acount.kargeth-online.de/login.php";
    public GUISkin[] Kargeth;
    public Texture aTexture;
    void OnGUI()
    {
        GUI.DrawTexture(new Rect(600,50,450,200), aTexture);
        if (GUI.Button(new Rect(1448, 850, 200, 50), "Zurück"))
        {
            Application.LoadLevel("_MainMenü");
        }
     UserID =  GUI.TextField(new Rect(725, 350, 200, 25), UserID,25);
      Password = GUI.PasswordField(new Rect(725, 400, 200, 25), Password, "*"[0]);
      if (GUI.Button(new Rect(725, 450, 200, 25), "LOGIN"))
      {
          StartCoroutine(Login());
      }
      else {
          if(Input.GetKeyDown(KeyCode.Return))
          StartCoroutine(Login());
      }

    
    }

    IEnumerator Login(){
        WWWForm Form = new WWWForm();
        Form.AddField("UserID", UserID);
        Form.AddField("Password", Password);
        WWW LoginAccountWWW = new WWW(LoginURL, Form);
        yield return LoginAccountWWW.error != null; 
        
        if (LoginAccountWWW.error != null)
        {
            Debug.LogError("Kann nicht zur Loginseite Verbinden. Bitte Kontaktieren sie den Support. Supportcode: 001");

        }else{
            Application.LoadLevel("_CharacterChange");
        }
    }

  
}

Documentation keeps doing

WWW www = new WWW(url);
yield return www;
...

rather than checking error. Manually, you’d check www.isDone.

Also WWW.error: “If there was no error, error will return null or an empty string (this is because some platforms don’t allow nulls for string values). We recommend that you use String.IsNullOrEmpty to check for the presence of an error so that both cases are covered.”