function checkAgreement() {
  var f = document.registerForm;
  f.submitButton.disabled = !( f.disclaimer.checked && f.principles.checked );
}
function checkFields() {
  var f = document.registerForm;
  var finished = ( f.disclaimer.checked && f.principles.checked && f.name.value!="" && f.email.value!="" );
  if(!finished) {
    alert("To continue, you must agree to the terms above,\nand provide your name and a valid email address.");
    return false;
  }
  return true;
}