WorldToScreenPoint(position: Vector3): Vector3;
Vector3 WorldToScreenPoint(Vector3 position);
def WorldToScreenPoint(position as Vector3) as Vector3

Transforms position from world space into screen space.

Screenspace is defined in pixels. The bottom-left of the screen is (0,0); the right-top is (pixelWidth,pixelHeight). The z position is in world units from the camera.
	var target : Transform;

function Update () { var screenPos : Vector3 = camera.WorldToScreenPoint (target.position); print ("target is " + screenPos.x + " pixels from the left"); }
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public Transform target;
    void Update() {
        Vector3 screenPos = camera.WorldToScreenPoint(target.position);
        print("target is " + screenPos.x + " pixels from the left");
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public target as Transform

	def Update() as void:
		screenPos as Vector3 = camera.WorldToScreenPoint(target.position)
		print((('target is ' + screenPos.x) + ' pixels from the left'))