Unity Facebook 400 Bad Request

I using following code to get user data from facebook

  IEnumerator UserFBDataGet(string accessTkn)
  {
   var  downloader3 = new WWW (  "https://graph.facebook.com/me?fields=id,name,email&access_token="+accessTkn  );
   //Application.OpenURL (  "https://graph.facebook.com/me?fields=id,name,email&access_token="+accessTkn  );
   yield return downloader3;
   print(" downloader3.text  ="+downloader3.text );
   if(downloader3.error == null)
   {
       print(" downloader3.text  ="+downloader3.text );
   }
   else
   {
       print(" downloader3.error  ="+downloader3.error );
   }
 }

Even i use WWWForm same error is showing

 IEnumerator UserFBDataGet(string accessTkn)
 {

   userDataGetUrl = "https://graph.facebook.com/me?";

   WWWForm  wf = new WWWForm();

   wf.AddField ("fields","id,name,email") ;
   wf.AddField ("access_token",accessTkn) ;

   WWW  downloader3 = new WWW(userDataGetUrl,wf) ;

   yield return downloader3;

   print(" downloader3.text  ="+downloader3.text );
         if(downloader3.error == null)
         {
             print(" downloader3.text  ="+downloader3.text );
         }
         else
         {
             print(" downloader3.error  ="+downloader3.error );
         }
    }

But when I call

 Application.OpenURL (  "https://graph.facebook.com/me?fields=id,name,email&access_token="+accessTkn  );

in that page i get all data properly.

It showing Error

You are trying to load data from a www stream which had the following error when downloading. 400 Bad Request UnityEngine.WWW:get_text() c__Iterator1:MoveNext() (at Assets/FBDesktopManager.cs:126)

You are trying to load data from a www stream which had the following error when downloading. 400 Bad Request UnityEngine.WWW:get_text() c__Iterator6:MoveNext() (at Assets/Scripts/FBDesktopManager.cs:91)