function validaEmail(email){

	var e = document.getElementById('erro_email');
	var f = document.getElementById('btn_cadastrar');

	if((email.value.indexOf("@") < 1) || (email.value.indexOf(".") < 1)){
		e.className = 'email_invalido';
		f.disabled = true;
	}
	else {
		e.className = 'email_valido';
		f.disabled = false;
	}
}