function validate(form) {
  if(form.first_name.value == "") {
    alert("Please enter a first name.");
    return false;
  }if(form.last_name.value == "") {
    alert("Please enter a last name.");
    return false;
  }if(form.email.value == "") {
    alert("Please enter an email address.");
    return false;
  }
  if(form.email.value.indexOf('@',0) < 0) {
    alert("Please enter a valid email address.");
    return false;
  }if(form.email.value.indexOf('.',0) < 1) {
    alert("Please enter a valid email address.");
    return false;
  }
  
  return true;
}