<!-- form validation -->
function isEmailAddr(email) {
  var result = false;
  var theStr = new String(email);
  var index = theStr.indexOf("@");
  if (index > 0)
  {
    var pindex = theStr.indexOf(".",index);
    if ((pindex > index+1) && (theStr.length > pindex+1))
	result = true;
  }
  return result;
}

function validRequired(formField,fieldLabel) {
	var result = true;

	if (formField.value == "") 	{
		alert('Veuillez remplir le champ "' + fieldLabel + '".');
		formField.focus();
		result = false;
	}

	return result;
}
function allDigits(str) {
	return inValidCharSet(str,"0123456789");
}

function validEmail(formField,fieldLabel,required) {
	var result = true;

	if (required && !validRequired(formField,fieldLabel))
		result = false;

	if (result && ((formField.value.length < 3) || !isEmailAddr(formField.value)) ) {
		alert("Votre adresse e-mail doit avoir la forme votrenom@domaine.com");
		formField.focus();
		result = false;
	}

  return result;

}

function validNum(formField,fieldLabel,required) {
	var result = true;

	if (required && !validRequired(formField,fieldLabel))
		result = false;

 	if (result)
 	{
 		if (!allDigits(formField.value))
 		{
 			alert('xxx "' + fieldLabel +'".');
			formField.focus();
			result = false;
		}
	}

	return result;
}

function validLength(formField,fieldLabel,length) {
	var result = true;

	if (formField.value.length < length) {
		alert('xxx');
		formField.focus();
		result = false;
	}

  return result;

}

<!-- form validation -->