simple health system

I need help with my simple health system. It has many errors in that need to be cleaned up.
This is my first health script and I need to know how I can get it to work like I want it to.

var health = 100.0;
private var dead = false;
var DamageA = -10.0;


function OnControllerColliderhit(hit : ControllerColliderHit)
{
	if(hit.gameObject.tag=="fireball")
	{
		 health + DamageA;
	}
}



function LateUpdate()

{
	if (0 > health)
	{
	dead = true;
	}

	
	if(dead) = true
	{
		transform.position = Vector3(0,0,0);
		dead = false;
	}
}

You didn’t describe what you wanted your script to achieve but I have made some guesses. The following is a version of the script which I believe has the syntax errors removed as well as some cleanup. Compare it line by line to your original and make sure you understand what and why each line was changed as needed:

var health:float = 100.0;
var DamageA:float = -10.0;
private var dead:boolean = false;

function OnControllerColliderHit(hit : ControllerColliderHit)
{
	if (hit.gameObject.tag == "fireball")
	{
		health  += DamageA;
	}
}

function LateUpdate()
{
	if (health <= 0)
	{
		dead = true;
	}

	if(dead == true)
	{
	    transform.position = Vector3(0,0,0);
	    dead = false;
	}
}