function verify() {
var themessage = "Bitte folgende Felder richtig ausfüllen: ";

if (document.form.vorname.value=="") {
themessage = themessage + " - Vorname";
}

if (document.form.name.value=="") {
themessage = themessage + " -  Nachname";
}

if (document.form.strasse.value=="") {
themessage = themessage + " -  Strasse";
}

if (document.form.haus_nr.value=="") {
themessage = themessage + " - Hausnummer";
}

if (document.form.nation.value=="") {
themessage = themessage + " -  Nation";
}

if (document.form.plz.value=="") {
themessage = themessage + " -  PLZ";
}

if (document.form.ort.value=="") {
themessage = themessage + " - Ort";
}

if (document.form.email_member.value=="") {
themessage = themessage + " -  E-Mail";
}

if (document.form.sex.value=="") {
themessage = themessage + " -  Geschlecht";
}

if (document.form.geb_tag.value=="") {
themessage = themessage + " - Geburtstag";
}

if (document.form.geb_monat.value=="") {
themessage = themessage + " -  Geburtsmonat";
}

if (document.form.geb_jahr.value=="") {
themessage = themessage + " -  Geburtsjahr";
}

if (document.form.blz.value=="") {
themessage = themessage + " - BLZ";
}

if (document.form.bank.value=="") {
themessage = themessage + " -  Bank";
}

if (document.form.ktonummer.value=="") {
themessage = themessage + " -  Kontonummer";
}

if (document.form.einziehung.value=="") {
themessage = themessage + " -  Checkbox Einzieh Ermächtigung";
}

if (document.form.checker.value=="") {
themessage = themessage + " -  Checkbox Kontakt";
}

//alert if fields are empty and cancel form submit
if (themessage == "Bitte folgende Felder richtig ausfüllen: ") {
document.form.submit();
}
else {
alert(themessage);
return false;
   }
}