There many ways,.
text boxes display content entered into them. Are you trying to hide information entered into a text box and save it off in a hidden var somewhere?
If so, you could probably do something like this on a key down event of a textbox.
<script>
function hideText(obj)
{
hiddenField = document.getElementById("myHiddenField");
hiddenField.value += obj.value;
obj.value = "";
}
</script>
&
First off, options for select aren't hidden. They are the things that actually get shown.
You could use a hidden field
<form action="#" method="POST">
<input type="text" name="textBox" />
<input type="hidden" name="hiddenName" value="someValue" />
<input type="submit" value="Submit" />
</form>