function createRequestObject() {
	var ro;
	var browser = navigator.appName;
	if(browser == "Microsoft Internet Explorer") {
		ro = new ActiveXObject("Microsoft.XMLHTTP");	
	} else {
		ro = new XMLHttpRequest();	
	}
	return ro;
}

var http = createRequestObject();

function representantes(n) {
	document.getElementById('contenido_representantes').innerHTML= '<center><img src="imagenes/ajax-loader.gif" width="66" height="66" vspace="200"></center>';
	http.open('get','datos_representantes.php?zona='+n);
	http.onreadystatechange = handleRepresentantes;
	http.send(null);
}

function handleRepresentantes () {
	if(http.readyState == 4) {
		var txt = http.responseText;
		if (txt == 'ERROR'){
			alert('La tabla de representantes produjo un error');
		} else {
			document.getElementById('contenido_representantes').innerHTML= txt;
		}
	}
}