Code:
<form id="form1" method="post" target="submitwindow">
<button type="button" value="Absenden" onclick="submitform()" />
<script type="text/javascript">
<!--
function submitform() {
window.open("submit.html","submitwindow","width=310,height=400")
document.getElementById('form1').submit();
}
-->
</script>
</form>
Ohne Garantie. Es kann gut sein, dass das aktuelle Browser blocken, weil das schon sehr an der Grenze zu Cross-Domain-Scripting wandelt