function isEmail(str) {
  // are regular expressions supported?
  var supported = 0;
  if (window.RegExp) {
    var tempStr = "a";
    var tempReg = new RegExp(tempStr);
    if (tempReg.test(tempStr)) supported = 1;
  }
  if (!supported) 
    return (str.indexOf(".") > 2) && (str.indexOf("@") > 0);

  var r1 = new RegExp("(@.*@)|(\\.\\.)|(@\\.)|(^\\.)");
  var r2 = new RegExp("^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$");

  return (!r1.test(str) && r2.test(str));
}

function checkemail()
{
	var frm = document.getElementById('inform');

	var em = document.getElementById('email');
	var adr = em.value;

	if (adr!=""){
		if (!isEmail(adr)){
			alert ("Neplatná emailová adresa !");
			return false;
			}
	}

	frm.submit();
	return true;
}

function btypsel(x)
{
	document.inform.byttyp[x].checked = true;
}