function formValidator(){
  // Make quick references to our fields
  var Make = document.getElementById('Make');
  var Model = document.getElementById('Model');
  var D1 = document.getElementById('D1');
  var D2 = document.getElementById('D2');
  var D3 = document.getElementById('D3');
  var search_postcode = document.getElementById('search_postcode');

  // Check each input in the order that it appears in the form!
    if(madeSelection(Make, "Please select a vehicle manufacturer")){
    if(madeSelection(Model, "Please select a vehicle model")){
      if(madeSelection(D1, "Please select a minimum price for your search")){
        if(madeSelection(D2, "Please select a maximum price for your search")){
          if(madeSelection(D3, "Please select the maximum distance from your location you are prepared to travel")){
            if(lengthRestriction(search_postcode, 6, 8)){
                return true;
            }
          }
        }
      }
    }
  }

  return false;

  }

  function madeSelection(elem, helperMsg){
  if(elem.selectedIndex == 0){
    alert(helperMsg);
    elem.focus();
    return false;
  }else{
    return true;
  }
  }

  function lengthRestriction(elem, min, max){
  var uInput = elem.value;
  if(uInput.length >= min && uInput.length <= max){
    return true;
  }else{
    alert("Please enter a valid postcode between " +min+ " and " +max+ " characters without spaces. Please use only letters and numbers.");
    elem.focus();
    return false;
  }
  }

  function clearDefault(el) {
  if (el.defaultValue==el.value) el.value = ""
  }