function obtieneObjetoXmlHttp(){
	var xmlHttp=null;
	try {
		// Firefox, Opera 8.0+, Safari
		xmlHttp=new XMLHttpRequest();
 	}
	catch (e){
		 //Internet Explorer
 		try {
		xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
		}
	catch (e){
		xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
  		}
 	}
	return xmlHttp;
}