function resetCheck() {
  var chk = window.confirm("Wollen Sie alle Eingaben löschen?");
  if (chk == true) {
    document.getElementById('name').className = 'vorbelegung';
    document.getElementById('email').className = 'vorbelegung';
    document.getElementById('betreff').className = 'vorbelegung';
    document.getElementById('nachricht').className = 'vorbelegung';
  }
  return (chk);
}

function nachricht() {
  document.write('<form action="./" method="post" onreset="return resetCheck();">');
  document.write('<p>');
  document.write('<input type="text" name="nam" value="Ihr Name" id="name" class="vorbelegung" onfocus="activate(this,\'Ihr Name\')" onblur="leave(this,\'Ihr Name\')" /><br />');
  document.write('<input type="text" name="em" value="Ihre E-Mail-Adresse" id="email" class="vorbelegung" onfocus="activate(this,\'Ihre E-Mail-Adresse\')" onblur="leave(this,\'Ihre E-Mail-Adresse\')" /><br />');
  document.write('<input type="text" name="be" value="Betreff" id="betreff" class="vorbelegung" onfocus="activate(this,\'Betreff\')" onblur="leave(this,\'Betreff\')" /><br />');
  document.write('<input type="text" name="homepage" class="vorbelegung" id="homepage"');
  document.write('<textarea name="na" cols="50" rows="10" id="nachricht" class="vorbelegung" onfocus="activate(this,\'Ihre Nachricht\')" onblur="leave(this,\'Ihre Nachricht\')">Ihre Nachricht</textarea><br />');
  document.write('<input type="submit" name="senden" value="Abschicken" class="button" onmouseover="this.className = \'hover\'" onmouseout="this.className = \'button\'" /> ');
  document.write('<input type="reset" value="Zur&uuml;cksetzen" class="button" onmouseover="this.className = \'hover\'" onmouseout="this.className = \'button\'" />');
  document.write('</p>');
  document.write('</form>');
}