David,
I've just been investigating a simular 'key-press' for the enter key. Substitute the 'space' key and
you should be in business.
Netscape browsers require you to "capture" the event before you can do anything with it where Internet Explorer does not. Also Netscape uses a little bit different way to pass the event to the function.
Here is some code that works in Netscape 4+, Netscape 6 and Internet Explorer 5 browsers. It detects When a key has been pressed and then displays the key and its ascii code. You will also notice that I place focus to the window after the alert, this is because Netscape 6 requires that so that you can detect the next key. Hope this helps and good luck.