Need help! Error in script.

Assets/Scripts/BackgroundParallax.cs(19,30): error CS0117: Camera' does not contain a definition for main'

 using UnityEngine;
 using System.Collections;
 
 public class BackgroundParallax : MonoBehaviour
 {
     public Transform[] backgrounds;                // Array of all the backgrounds to be parallaxed.
     public float parallaxScale;                    // The proportion of the camera's movement to move the backgrounds by.
     public float parallaxReductionFactor;        // How much less each successive layer should parallax.
     public float smoothing;                        // How smooth the parallax effect should be.
 
 
     private Transform cam;                        // Shorter reference to the main camera's transform.
     private Vector3 previousCamPos;                // The postion of the camera in the previous frame.
 
 
     void Awake ()
     {
         // Setting up the reference shortcut.
         cam = Camera.main.transform;
     }
 
 
     void Start ()
     {
         // The 'previous frame' had the current frame's camera position.
         previousCamPos = cam.position;
     }
 
 
     void Update ()
     {
         // The parallax is the opposite of the camera movement since the previous frame multiplied by the scale.
         float parallax = (previousCamPos.x - cam.position.x) * parallaxScale;
 
         // For each successive background...
         for(int i = 0; i < backgrounds.Length; i++)
         {
             // ... set a target x position which is their current position plus the parallax multiplied by the reduction.
             float backgroundTargetPosX = backgrounds[i].position.x + parallax * (i * parallaxReductionFactor + 1);
 
             // Create a target position which is the background's current position but with it's target x position.
             Vector3 backgroundTargetPos = new Vector3(backgroundTargetPosX, backgrounds[i].position.y, backgrounds[i].position.z);
 
             // Lerp the background's position between itself and it's target position.
             backgrounds[i].position = Vector3.Lerp(backgrounds[i].position, backgroundTargetPos, smoothing * Time.deltaTime);
         }
 
         // Set the previousCamPos to the camera's position at the end of this frame.
         previousCamPos = cam.position;
     }
 }

Assets/Scripts/BackgroundParallax.cs(19,30): error CS0117: Camera' does not contain a definition for main'