var url_base = "http://127.0.0.1/desarrollo/caniexpress/";

			var READY_STATE_UNINITIALIZED = 0; 
			var READY_STATE_LOADING = 1; 
			var READY_STATE_LOADED = 2;
			var READY_STATE_INTERACTIVE = 3; 
			var READY_STATE_COMPLETE = 4;
		
			
						// Éste es el objeto que permite interactuar con el servidor
			var net = new Object();
			 
			net.READY_STATE_UNINITIALIZED=0; 
			net.READY_STATE_LOADING=1; 
			net.READY_STATE_LOADED=2; 
			net.READY_STATE_INTERACTIVE=3; 
			net.READY_STATE_COMPLETE=4; 
			 
			// Constructor
			net.CargadorContenidos = function(url, funcion, funcionError, metodo, parametros, contentType) {
			  this.url = url;
			  this.req = null;
			  this.onload = funcion;
			  this.onerror = (funcionError) ? funcionError : this.defaultError;
			  metodo = (metodo) ? metodo : 'GET';
			  this.cargaContenidoXML(url, metodo, parametros, contentType);
			}
			 
			net.CargadorContenidos.prototype = {
			  cargaContenidoXML: function(url, metodo, parametros, contentType) {


//			    if(window.XMLHttpRequest) {
			   if (navigator.appName == "Netscape") { 
			      this.req = new XMLHttpRequest();
			      this.req.overrideMimeType('text/xml');
			      
//			    }  else if(window.ActiveXObject) {
			    }  else {
	
//			    alert('caca');
			      this.req = new ActiveXObject('Microsoft.XMLHTTP');
			    }
			 
			    if(this.req) {
			      try {
			        var loader = this;
			        this.req.onreadystatechange = function() {
			          loader.onReadyState.call(loader);
			        }
			        this.req.open(metodo, url, true);
			        if(contentType) {
			          this.req.setRequestHeader('Content-Type', contentType);
			        }
			        this.req.send(parametros);
			        } catch(err) {
			          this.onerror.call(this);
			        }
			    }
			  },
			 
			  onReadyState: function() {
			    var req = this.req; 
			    var ready = req.readyState; 
			    if(ready == net.READY_STATE_COMPLETE) { 
			      var httpStatus = req.status; 
			      if(httpStatus == 200 || httpStatus == 0) { 
			        this.onload.call(this);
			      }
			      else {
			        this.onerror.call(this);
			      }
			    }
			  },
			 
			  defaultError: function() {
				alert('error');
			  }
			}