function busca(act,cat){
var obj = document.getElementById('conteudo');
req = null;

if(act=="buscaCarro"){
                      url = "__ajax/buscaCarro.php?i="+cat;
                      document.getElementById("dvmodelo").innerHTML='<select name="modelo" id="modelo" style="width:222px"><option value="">Carregando modelos...</option></select>';
} else
if(act=="buscaMoto"){
                      url = "__ajax/buscaMoto.php?i="+cat;
                      document.getElementById("dvmodelo").innerHTML='<select name="modelo" id="modelo" style="width:222px"><option value="">Carregando modelos...</option></select>';
}

if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
req.onreadystatechange = processReqChange;
req.open("GET",url,true);
req.send(null);
} else if (window.ActiveXObject) {
req = new ActiveXObject("Microsoft.XMLHTTP");
if (req) {
req.onreadystatechange = processReqChange;
req.open("GET",url,true);
req.send();
}
} else {
function getHTTPObject() {
var req;
try {
 if (window.XMLHttpRequest) {
  req = new XMLHttpRequest();
  if (req.readyState == null) {
   req.readyState = 1;
   req.addEventListener("load", function () {
   req.readyState = 4;
   if (typeof req.onReadyStateChange == "function")
    req.onReadyStateChange();
   }, false);
  }
  return req;
 }
 if (window.ActiveXObject) {
  var prefixes = ["MSXML2", "Microsoft", "MSXML", "MSXML3"];
  for (var i = 0; i < prefixes.length; i++) {
   try {
    req = new ActiveXObject(prefixes[i] + ".XmlHttp");
    return req;
   } catch (ex) {};
  }
 }
} catch (ex) {}
alert("XmlHttp Objects not supported by client browser");
}
req.onreadystatechange = processReqChange;
req.open("GET",url,true);
req.send();
}
}
function processReqChange(){
obj = document.getElementById("dvmodelo");
if (req.readyState == 4) {
if (req.status ==200) {
if(req.responseText==""){
  obj.innerHTML = "<font color=\"#ff0000\"><i>Nenhuma informação cadastrada</i></font>";
} else {
     obj.innerHTML = req.responseText;
}
} else {
  obj.innerHTML = "Houve um problema ao obter os dados";
}
}
}

// ---------------------------------------------------------------------------------------------