Button and resolution problem

Hello I have a big problem. button change place after a build the project and change the resolution. in unity i work with 1200 * 700 resolution (( 16/9 )) but when a change other resolution or make it iu full screen the button change place. not the same when i put it in unity project. how can i fix that . thanks

GUI positions are absolute meaning that they will change their relative position if the screen size changes. To make them relative you need to calculate your Rectangles using factors. eg.:

void OnGUI () {
  public float x, y, width, height;
  Rect pos;
  pos.x = x * Screen.width;
  pos.y = y * Screen.height;
  pos.width = width * Screen.width;
  pos.height = height * Screen.height;

  GUI.Button(pos, "test");
}

With x, y, width and height being values between 0...1 this should lead to relative positioning.