function init() {
  ClearSelection(document.carSelect.year,"- Select A Year -");
  ClearSelection(document.carSelect.make,"- Select A Make -");
  ClearSelection(document.carSelect.model,"- Select A Model -");
  var year="";
  var Selection=document.carSelect.year;
  for (year in cars) {
    Selection.options[Selection.options.length]=new Option(year,year,false,false);
  }
  Selection.options[0].selected=true;
  document.carSelect.make.options[0].selected=true;
  document.carSelect.model.options[0].selected=true;
}

function verify() {
  var year=getYear();
  var model=getModel();
  var make=getMake();
  var mesg="";
  if (year == "") {
    mesg=mesg+"You must select a year!\n";
  }
  if (make == "") {
    mesg=mesg+"You must select a make!\n";
  }
  if (model == "") {
    mesg=mesg+"You must select a model!\n";
  }
  if (mesg != "") {
    mesg="Error!\n\n"+mesg;
	alert(mesg);
	return false;
  } else {
    return true;
  }
}

function ClearSelection(Selection, newOption) {
  Selection.length=0;
  Selection.options[0]=new Option(newOption, '',true,true);
}

function getYear() {
  var Years=document.carSelect.year;
  for (var i=0; i < Years.options.length; i++) {
    if (Years.options[i].selected) {
	  return Years.options[i].value;
	}
  }
}

function getMake() {
  var Makes=document.carSelect.make;
  for (var i=0; i < Makes.options.length; i++) {
    if (Makes.options[i].selected) {
      return Makes.options[i].value;
	}
  }
}

function getModel() {
  var Models=document.carSelect.model;
  for (var i=0; i < Models.options.length; i++) {
    if (Models.options[i].selected) {
	  return Models.options[i].value;
	}
  }
}

function YearSelected() {
  ClearSelection(document.carSelect.make,"- Select A Make -");
  ClearSelection(document.carSelect.model,"- Select A Model -");
  var make="";
  var year=getYear();
  for (make in cars[year]) {
    var Selection=document.carSelect.make;
	Selection.options[Selection.options.length]=new Option(make, make,false,false);
  }
  document.carSelect.make.options[0].selected=true;
}

function MakeSelected() {
  ClearSelection(document.carSelect.model,"- Select a Model -");
  var make=getMake();
  var year=getYear();
  var model="";
  for (model in cars[year][make]) {
    var Selection=document.carSelect.model;
	Selection.options[Selection.options.length]=new Option(model, model,false,false);
  }
  document.carSelect.model.options[0].selected=true;
}

function ModelSelected() {
  var make=getMake();
  var year=getYear();
  var model=getModel();
}