UnityEngine.Application.LoadLevel(String) is obsolet!

When trying to work my main menu for one of my creations, I was repeatedly getting this error/warning, that did although lead into a larger problem. I do not understand what I am doing wrong... If anyone can help, it would be greatly appreciated... The error occurs on line 10 below

 function OnGUI(){
     if(menu){
             GUI.Box(new Rect(Screen.width /2 -100,Screen.height /2 -120,200,160), "Game Over");
             if(GUI.Button(new Rect(Screen.width /2 -80,Screen.height /2 -80,160,40), "Retry")) {
                 LoadData();
             }
             if(GUI.Button(new Rect(Screen.width /2 -80,Screen.height /2 -20,160,40), "Quit Game")) {
                 mainCam = GameObject.FindWithTag ("MainCamera").transform;
                 Destroy(mainCam.gameObject); //Destroy Main Camera
                 Application.LoadLevel ("Title");
                 //Application.Quit();
             }
     }
 }