function get_model(marqu){
  var xhr=null;

    if (window.XMLHttpRequest) {
        xhr = new XMLHttpRequest();
    }
    else if (window.ActiveXObject)
    {
        xhr = new ActiveXObject("Microsoft.XMLHTTP");
    }
    xhr.open("GET", "scripts/models.php?id="+marqu, false);
    xhr.send(null);
   document.getElementById('mod').innerHTML=xhr.responseText;
}