window.onload = function() {
yearbox = document.getElementById('years');
yearbox.selectedIndex = 0;
}

function populate(step, destbox) {

yearbox = document.getElementById('years');
modelbox = document.getElementById('models');
makebox = document.getElementById('makes');


if (step < 2) {
var params = "year="+yearbox.options[yearbox.selectedIndex].value;
//modelbox.innerHTML = "<option value=\"Make\">Make</option>";
modelbox.disabled = true;
} else {
var params = "year="+yearbox.options[yearbox.selectedIndex].value+"&make="+makebox.options[makebox.selectedIndex].value;
}

page = "populate_csv.php?"+params;

//document.getElementById(destbox).innerHTML="<option value=\"Loading\">Loading</options>";

$.ajax({
  url: page,
  success: function(data) {
opts = data.split(",");
for(var i=0;i<opts.length-1;i++) {
document.getElementById(destbox).options[i] = new Option(opts[i],opts[i]);
}
document.getElementById(destbox).disabled = false;
if (step < 2) {populate(2, 'models');}  }, type: 'GET'});

}