Key Press

How can I trap which key is being pressed on a document.
I can get it to display a message when a key has been pressed, but I need to trap just certain keys using Javascript.

Help!!

I'm pretty sure this is IE, not sure about Netscape...

Code:

---

<script LANGUAGE = "JavaScript">
function showKey(){
alert(event.keyCode);
}

document.onkeypress = showKey;

</script>

---

Just hit the key you want to find out the keycode...