function validate(f) {
  if (f.name.value == "") {
    alert("Please enter your name");
    f.name.focus();
    return false;
  }

  if (f.email.value == "") {
    alert("Please enter your email address");
    f.email.focus();
    return false;
  }

  if (isEmail(f.email.value) == false) {
    alert("Please enter a valid email address\ne.g. name@company.com.au");
    f.email.select();
    return false;
  }

  if (f.message.value == "") {
    alert("Please enter your message");
    f.message.focus();
    return false;
  }
  return true;
}

function isEmail(string) {
  return (string.search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/) != -1);
}