function check() {
var emailExp=/^[\w\.=-]+@[\w\.-]+\.[\w]+$/;
var nameExp=/^[\w\-\.]+[\w\-\.\ ]+$/;

var name=document.getElementById('name').value;
var email=document.getElementById('email').value;
var leiras=document.getElementById('leiras').value;
if (name=="")) {
	document.getElementById("alert_name").style.visibility='visible';
	if (email!="" && email.match(emailExp)) {
		document.getElementById("alert_email").style.visibility='hidden';
	} else {
		document.getElementById("alert_email").style.visibility='visible';
	} 
	if (leiras!="") {
		document.getElementById("alert_leiras").style.visibility='hidden';
	} else {
		document.getElementById("alert_leiras").style.visibility='visible';
	} 
	return false;
	} else if (email=="" || !document.getElementById("email").value.match(emailExp)) {
	document.getElementById("alert_name").style.visibility='hidden';
	if (leiras!="") {
		document.getElementById("alert_leiras").style.visibility='hidden';
	} else {
		document.getElementById("alert_leiras").style.visibility='visible';
	} 
	document.getElementById("alert_email").style.visibility='visible';
	return false;
	} else if (leiras=="") {
	document.getElementById("alert_name").style.visibility='hidden';
	document.getElementById("alert_email").style.visibility='hidden';
	document.getElementById("alert_leiras").style.visibility='visible';
	return false;
	} else {
	return true;
	}
}