function checkGuestbookForm(form) {
	var emptyData = false;
	var text = "";
	var emailRegExp = /^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.([a-z]){2,4})$/;

	if (form.author.value==""){
		emptyData = true;
		text += " Autor,";
	} else {
		if (!emptyData) {
			emptyData = false;
		}
	}

	if (form.email.value != "") {
		if (emailRegExp.test(form.email.value)==true && form.email.value.length!=0) {
			if (!emptyData) {
				emptyData = false;
			}
		} else {
			text += " Email,";
			emptyData = true;
		}
	}

	if (form.securitycode.value==""){
		emptyData = true;
		text += " Kod z obrazka,";
	} else {
		if (!emptyData) {
			emptyData = false;
		}
	}
	
	if (form.content.value==""){
		emptyData = true;
		text += " Treść wpisu,";
	} else {
		if (!emptyData) {
			emptyData = false;
		}
	}

	if (!emptyData) {
		return true;
	} else {
		document.getElementById('info-guestbook').innerHTML = "Prosze wprowadzic poprawnie pozycje: " + text.substr(0,text.length - 1);
		return false;
	}
}