function checkonSubmit() {
  var correct = 0;
  var re = new RegExp(/^([a-zA-Z0-9_.-])+@([a-zA-Z0-9_.-])+\.([a-zA-Z])+([a-zA-Z])+/);

  // Reset the color for background and text color;

  reset();

  if (document.getElementById('visitor').value == ''){
    document.getElementById('visitor').style.backgroundColor = 'Grey';
    document.getElementById('visitor').style.color = 'White';
    correct = 1;
  }

  if (document.getElementById('visitormail').value == '' || !document.getElementById('visitormail').value.match(re)){
    document.getElementById('visitormail').style.backgroundColor = 'Grey';
    document.getElementById('visitormail').style.color = 'white';
    correct = 1;
  }

  if (document.getElementById('comments').value == ''){
    document.getElementById('comments').style.backgroundColor = 'Grey';
    document.getElementById('comments').style.color = 'white';
    correct = 1;
  }

  if (correct == 1){
    document.getElementById('errorMessage').style.display = '';
    return false;  //Force form to give up submit if anything goes wrong;
  }
  return true;
}

function reset(){
  document.getElementById('visitor').style.backgroundColor = 'White';
  document.getElementById('visitormail').style.backgroundColor = 'White';
  document.getElementById('comments').style.backgroundColor = 'White';

  document.getElementById('visitor').style.color = 'black';
  document.getElementById('visitormail').style.color = 'black';
  document.getElementById('comments').style.color = 'black';
}