var whitespace = " \t\n\r";

	function isEmpty(s) {
	    return ((s == null) || (s.length == 0));
	}

	function isWhitespace (s) {
		var i;
		if (isEmpty(s)) return true;
		for (i = 0; i < s.length; i++)
		{   
			var c = s.charAt(i);
			if (whitespace.indexOf(c) == -1) return false;
		}
		return true;
	}

	function isEmail (s) {
		var i = 1;
		var sLength = s.length;
		while ((i < sLength) && (s.charAt(i) != "@")) { i++ }
		if ((i >= sLength) || (s.charAt(i) != "@")) return false;
		else i += 2;
		while ((i < sLength) && (s.charAt(i) != ".")) { i++ }
		if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
		else return true;
	}


	function checkString (theField) {
		var ok = true;
		if (theField == null) ok = false;
		if (isEmpty(theField.value)) ok = false;
		if (isWhitespace(theField.value)) ok = false;
		return ok;
	}

	function checkEmail (theField) {
		var ok = true;
		if (isEmpty(theField.value)) ok = false;
		if (!isEmail(theField.value)) ok = false;
		return ok;
	}

	function K() {
		form = document.F;
	   	ok = 
		  checkString(form.elements["jmeno"]) &&
		  checkString(form.elements["firma"]) &&
		  checkString(form.elements["funkce"]) &&
		  checkString(form.elements["cinnost"]) &&
		  checkString(form.elements["ulice"]) &&
		  checkString(form.elements["psc"]) &&
		  checkString(form.elements["mesto"]);
		  
		  if (!ok) { alert(warnEmpty); }
		  else {
		  	ok = (checkEmail(form.elements["email"]));
				if (!ok) { alert(warnEmail); }
		  }	 
			return(ok);
	}