<script type="text/javascript">
function check (id, sbm) {
if (document.getElementById(id).value == '666') document.getElementById(sbm).style.display = '';
};
</script>
<form>
<input type="text" id="pole">
<input type="button" onclick="check('pole','sbm');">
<input type="submit" id="sbm" style="display:none">
</form>