<form name=form1 onsubmit="meizz()">
<input type="submit" value="ok">
</form>
<script language=javascript>
function meizz()
{
  var e = document.form1;
  e.action = "a.asp";
  e.target = "target1"; //指定target 值是防止都提交到一个网页里发生冲突
  e.submit();

  e.action = "b.asp";
  e.target = "target2";
  e.submit();
}
</script>
<iframe name="target1" width=1 height=1></iframe><!--也可以用隐藏属性试试-->
<iframe name="target2" width=1 height=1></iframe>

但是如果本页有跳转的话，建议先跳转iframe，然后setTimeout 1秒再跳转本页