var ajax;
var codigo = 0;

function changeBackground(obj, img){
		document.getElementById(obj).style.backgroundImage= "url('images/"+img +"')";  
}

function changeImage(obj, img){
		document.getElementById(obj).src = "images/"+img;  
}

function objetoAjax(){
	if (window.XMLHttpRequest){ // code for IE7+, Firefox, Chrome, Opera, Safari
		return new XMLHttpRequest();
	}
	if (window.ActiveXObject){ // code for IE6, IE5
		return new ActiveXObject("Microsoft.XMLHTTP");
	}
	return null;
}