Press any key to determine the javascript key code of that key. This is a simple script: 
<script language="JavaScript">
document.onkeydown = checkKeycode
function checkKeycode(e) {
var keycode;
if (window.event) keycode = window.event.keyCode;
else if (e) keycode = e.which;
alert("keycode: " + keycode);
}
</script>
You may also use this sort of function to disable certain keys, by adding a void(0) in the function as shown. This essentially tells the page to cancel the last event, e.g. the pressing of that certain key. In the example below, the key that is disabled is the enter key. 
<script language="JavaScript">
document.onkeydown = checkKeycode
function checkKeycode(e) {
var keycode;
if (window.event) keycode = window.event.keyCode;
else if (e) keycode = e.which;
if(keycode == 13){
void(0);
}
}
</script>