GetAxis main thread issues

So I'm working on half of a mouselook script. But I keep running into the error "GetAxis can only be executed in the main thread"

I've tried everything I can, stuff I've tried has a number next to it for reference.

 #pragma strict
 var mouseX = Input.GetAxis("Mouse X"); 1
 var mouseX = Input.GetAxis("Mouse X") * Time.deltaTime; 2
 
 function Start () {
     var mouseX = Input.GetAxis("Mouse X"); 3
     Screen.lockCursor = true;
 }
 
 function Update () {
     var mouseXcompile = mouseX * Time.deltaTime; 4
     transform.Rotate(mouseXcompile, 0, 0);
 }

4 obviously isn't there when 2 is. If I do 3, I get tons of errors.