Javascript error

I write a javascript whit simple variables but when i compile it send error mesage : x is not a member of object.

 #pragma strict
 
 var Alap : Texture2D;
 var GUIMenu : GUISkin;
 var MainOn = false;
 var x:int;
 var y:int;
 var resolution;
 
 function Start () {
     MainOn = true;
     resolution= new Vector2(Screen.width, Screen.height);
     x=Screen.width/1920.0f;
     y=Screen.height/1080.0f;
 }
 
 function Update () {
     if(Screen.width != resolution.x || Screen.height!=resolution.y)
     {
         resolution=new Vector2(Screen.width, Screen.height);
         x=resolution.x/1920.0f;
         y=resolution.y/1080.0f;
         
     }
 
 }
 
 function OnGUI()
 {
     if(MainOn == true)
     {
         GUI.skin = GUIMenu;
         GUI.DrawTexture(Rect(0,0,Screen.width,Screen.height), Alap, ScaleMode.StretchToFill, true, 0.0f);
         GUI.Label(Rect(150*x,30*y,200,100), "Valse");
         if(GUI.Button(Rect(110*x,200*y,110,35), "Játék indítása")){            
         }
         if(GUI.Button(Rect(110*x,240*y,110,30), "Beállítások")){            
         }
         if(GUI.Button(Rect(110*x,280*y,110,30), "Kilépés")){
             Application.Quit();            
         }
     }
 }