function check() 
{
	var REG_MAIL = /^[\w-\.]{2,}@[\w-]{1,}\./;

	if(!REG_MAIL.test(document.email_form.email.value)) 
	{
		alert(invalidMailMsg);
		document.email_form.email.focus();
	} 
	else 
	{
		var url = "https://secure.securitetotale.com/cb.php?module=guest_cbsys_preform&w=0&force_step1=1&action=step2&email=" + document.email_form.email.value + "&id=" + id + "&idp=1&mb&tracker=" + tracker + "&synergie=" + synergie + "&param=&num_facturation=1&oldrf=" + oldrf + "&rf=" + rf + "&id_site=" + id_site + "&id_produit=" + id_produit + "&langue=" + langue;
		if (typeof id_facturation != 'undefined')
		{
			url += "&id_facturation=" + id_facturation;
		}

		window.open(url);
	}
}