function validateComment() {
  hideCommentForm();

  var error = "";
  var grade = document.getElementById("add-comment-grade");
  var comment = document.getElementById("add-comment-comment");

  error = "You must select a grade";
  if(grade.value == "" || grade.value == 0) {
    document.getElementById("grade-error").innerHTML = error;
    grade.focus();
    return false;
  }

  error = "You must enter a comment";
  if(comment.value == "") {
    document.getElementById("comment-error").innerHTML = error;
    comment.focus();
    return false;
  }

  return true;
}

function hideCommentForm() {
  document.getElementById("grade-error").innerHTML = "";
  document.getElementById("comment-error").innerHTML = "";
}