function trim(str) {
  return str.replace(/^\s*|\s*$/g,"");
}

function CheckEmail(field) {
  var filter = /^[-A-Za-z0-9_\+\.]+@([A-Za-z0-9\-]+\.)+[A-Za-z]{2,4}$/;

  var is_ok = filter.test(field.value);

  if (!is_ok) {
    field.focus();
  }
  return is_ok;
}

function CheckTextField(inTextField) {
  var is_ok = (trim(inTextField.value) != "") && (inTextField.value != "undefined");

  if (!is_ok) {
    inTextField.focus();
  }
  return is_ok;
}

function CheckUploadForm(form) {
  if (!CheckTextField(form.name)) {
    alert("Name is required.");
    return false;
  }

  if (!CheckEmail(form.email)) {
    alert("Please enter a valid e-mail address.");
    return false;
  }

  if (!CheckTextField(form.comment_text)) {
    alert("Comment is required.");
    return false;
  }

  if (!CheckTextField(form.code)) {
    alert("Verification code is required.");
    return false;
  }

  return true;
}