// Instancia un nuevo objeto XMLHttpRequest
function obtenerXHR(){
	req = false;
	if(window.XMLHttpRequest){
		req=new XMLHttpRequest();
	} else {
			if(ActiveXObject)
			{
				var vectorVersiones =["MSXML2.XMLHttp.5.0","MSXML2.XMLHttp.4.0","MSXML2.XMLHttp.3.0","MSXML2.XMLHttp","Microsoft.XMLHttp"];
				for(var i=0;i<vectorVersiones.length;i++)
				{
					try{
						req=new ActiveXObject(vectorVersiones[i]);
						return req;
					} catch (e){}
				}
			}
	}
	return req;
}