Computer help needed!

[pebblerocker]

How can I disable the space bar behaving as a second "page down" key? It's the one key most likely to be lain on by a cat, and it's getting frustrating when I'm reading long pages. Leading experts (my personal geek) have tried and failed to answer this. It's built into Firefox, Internet Explorer, Safari and Opera, so it seems there's no simple way of getting away from it.

Moving the cat off the desk has been tried repeatedly. Standing the keyboard up on its end beside the monitor is one solution, but rather inconvenient.