function chkFormular () {

if (document.calc.vorname.value == "") {
    alert("Please fill in your first name!");
    document.calc.vorname.focus();
    return false;
  }

if (document.calc.nachname.value == "") {
    alert("Please fill in your last name!");
    document.calc.nachname.focus();
    return false;
  }

if (document.calc.strasse.value == "") {
    alert("Please write down your street address!");
    document.calc.strasse.focus();
    return false;
  }

if (document.calc.ort.value == "") {
    alert("Please write down your hometown address!");
    document.calc.ort.focus();
    return false;
  }

if (document.calc.plz.value == "") {
    alert("Please write your postcode!");
    document.calc.plz.focus();
    return false;
  }

if (document.calc.country.value == "") {
    alert("Please write your country!");
    document.calc.country.focus();
    return false;
  }

if (document.calc.absender.value.indexOf("@") == -1) {
    alert("Please fill in your mailing address!");
    document.calc.absender.focus();
    return false;
  }

}