// JavaScript Document
function Inint_AJAX() {
   try { return new ActiveXObject("Msxml2.XMLHTTP");  } catch(e) {} //IE
   try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch(e) {} //IE
   try { return new XMLHttpRequest();          } catch(e) {} //Native Javascript
   alert("XMLHttpRequest not supported");
   return null;
};

function dochange(src, val) {
     var req = Inint_AJAX();
     req.onreadystatechange = function () { 
          if (req.readyState==4) {
               if (req.status==200) {
                    document.getElementById(src).innerHTML=req.responseText; //retuen value
               } 
          }
     };
     req.open("GET", "includes/vehicle.php?data="+src+"&val="+val); //make connection
     req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=iso-8859-1"); // set Header
     req.send(null); //send value
}

window.onLoad=dochange('types', -1);         // value in first dropdown