function checkForm() {
if (document.form_rejestracja.imie.value.length <= 0) {
						alert ("Please write your first name");
						document.form_rejestracja.imie.focus();
						return false;
						}
if (document.form_rejestracja.nazwisko.value.length <= 0) {
						alert ("Please write your surname");
						document.form_rejestracja.nazwisko.focus();
						return false;
						}
if (document.form_rejestracja.email.value.length <= 0) {
						alert ("Please write your email");
						document.form_rejestracja.email.focus();
						return false;
						}
if (isDate(document.form_rejestracja.data_urodzenia.value)==false){
					document.document.form_rejestracja.data_urodzenia.focus();
					return false;
					}if (document.form_rejestracja.adres_ul.value.length <= 0) {
						alert ("Please write your address");
						document.form_rejestracja.adres_ul.focus();
						return false;
						}
if (document.form_rejestracja.adres_kod.value.length <= 0) {
						alert ("Please write your postcode");
						document.form_rejestracja.adres_kod.focus();
						return false;
						}
if (document.form_rejestracja.adres_miasto.value.length <= 0) {
						alert ("Please write your city");
						document.form_rejestracja.adres_miasto.focus();
						return false;
						}
if (document.form_rejestracja.adres_kraj_id.value.length <= 0) {
						alert ("Please choose your country");
						document.form_rejestracja.adres_kraj_id.focus();
						return false;
						}

}


var dtCh= "-";
var minYear=1900;
var maxYear=2100;

function isInteger(s){
	var i;
	for (i = 0; i < s.length; i++){   
		// Check that current character is number.
		var c = s.charAt(i);
		if (((c < "0") || (c > "9"))) return false;
	}
	// All characters are numbers.
	return true;
}

function stripCharsInBag(s, bag){
	var i;
	var returnString = "";
	// Search through string's characters one by one.
	// If character is not in bag, append to returnString.
	for (i = 0; i < s.length; i++){   
		var c = s.charAt(i);
		if (bag.indexOf(c) == -1) returnString += c;
	}
	return returnString;
}

function daysInFebruary (year){
	// February has 29 days in any year evenly divisible by four,
	// EXCEPT for centurial years which are not also divisible by 400.
	return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
}
function DaysArray(n) {
	for (var i = 1; i <= n; i++) {
		this[i] = 31;
		if (i==4 || i==6 || i==9 || i==11) {this[i] = 30;}
		if (i==2) {this[i] = 29;}
   } 
   return this;
}

function isDate(dtStr){
	var daysInMonth = DaysArray(12);
	var pos1=dtStr.indexOf(dtCh);
	var pos2=dtStr.indexOf(dtCh,pos1+1);
	var strYear=dtStr.substring(0,pos1);
	var strMonth=dtStr.substring(pos1+1,pos2);
	var strDay=dtStr.substring(pos2+1);
	strYr=strYear;
	if (strDay.charAt(0)=="0" && strDay.length>1) strDay=strDay.substring(1);
	if (strMonth.charAt(0)=="0" && strMonth.length>1) strMonth=strMonth.substring(1);
	for (var i = 1; i <= 3; i++) {
		if (strYr.charAt(0)=="0" && strYr.length>1) strYr=strYr.substring(1);
	}
	month=parseInt(strMonth);
	day=parseInt(strDay);
	year=parseInt(strYr);
	if (pos1==-1 || pos2==-1){
		alert("Improper date format; should be: yyyy-mm-dd");
		return false;
	}
	if (strMonth.length<1 || month<1 || month>12){
		alert("Please write proper month");
		return false;
	}
	if (strDay.length<1 || day<1 || day>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month]){
		alert("Please write proper day");
		return false;
	}
	if (strYear.length != 4 || year==0 || year<minYear || year>maxYear){
		alert("Please write proper year");
		return false;
	}
	if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false){
		alert("Please write proper date");
		return false;
	}
return true;
}