function xmlhttpPost(strURL) {

    var xmlHttpReq = false;

    var self = this;

	var colonias;

	var divResultado = document.getElementById("coloniaMensaje");

	

    // Mozilla/Safari

    if (window.XMLHttpRequest) {

        self.xmlHttpReq = new XMLHttpRequest();

    }

    // IE

    else if (window.ActiveXObject) {

        self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");

    }



	

	var selectF = document.getElementById('selectF');

    selectF.options.length = 0;

   	

	self.xmlHttpReq.open('POST', strURL, true);

    self.xmlHttpReq.onreadystatechange = function() {

		if(self.xmlHttpReq.readyState ==1){

						//divResultado.innerHTML = "<img src='../_imagenes/icons/carga.gif' alg='cargando...'>";

						divResultado.innerHTML = "<b>Cargando colonias ...</b>";

                } else

        if (self.xmlHttpReq.readyState == 4) {

			

			  if(self.xmlHttpReq.status==200)

                   {

                     colonias = self.xmlHttpReq.responseText.split("|");



						var opt = document.createElement("option");

						opt.text = "Todas las colonias disponibles";

				        opt.value = "0";

						selectF.options.add(opt);



					for(i=0;i < colonias.length-1;i++)

				      {

						var opt = document.createElement("option");

						opt.text = colonias[i];

				        opt.value = colonias[i];

						selectF.options.add(opt);

					

					  }

						divResultado.innerHTML = " ";

                   }

				    else if(self.xmlHttpReq.status==404)

                                             {

			 				divResultado.innerHTML = "Colonias no definidas";

                                             }

                           else

                                             {

			 				divResultado.innerHTML = "Error:".self.xmlHttpReq.status;

                                             }

 			 

		        }

    }

    self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');

    self.xmlHttpReq.send(getquerystring());

}



function getquerystring() {

    var form = document.forms['form4'];

    var id = form.txtmunicipio.value;

    qstr = 'id=' + escape(id);  // NOTE: no '?' before querystring

    return qstr;

}