Assets/BGLooper.cs(20,29): error CS0120: An object reference is required to access non-static member `UnityEngine.Component.tag'

using UnityEngine;
using System.Collections;

public class BGLooper : MonoBehaviour {

int numBGPanels = 6;

float PipeMax = 6.19f;
float PipeMin = 3.86f;

void OnTriggerEnter2D(Collider2D collider){
	Debug.Log ("Triggered: " + collider.name);

	float widthofBGObject = ((BoxCollider2D)collider).size.x;

	Vector3 pos =  collider.transform.position;

	pos.x +=widthofBGObject * numBGPanels;

	if(Collider.tag == "Pipe") {**ERROR**
		pos.y = Random.Range(PipeMin, PipeMax);**ERROR**
		
	}

	collider.transform.position = pos ;

	}

}

if(Collider.tag == “Pipe”)
should be

 if(collider.tag == "Pipe") 

Note the upper/lower case of the C in collider.