function validate(){
	var submit = document.getElementById ('submit');
	var username = document.getElementById ('username');
	var comment = document.getElementById ('comment');
	var email = document.getElementById ('email');
	var phone = document.getElementById ('phone');
	if (!submit || !username || !comment || !email || !phone) return;
	submit.disabled = comment.value == '' || phone.value == '' || email.value == '' || username.value == ''; 
}