* Not every keyboard has Page Up/Down keys. As an application designer you can't rely on their presence.
* The spacebar is the largest key. For an application, it makes sense to attach commonly used functionality to this key. For media players this is pause/play. For web browsers this is "scroll down a page", as you'll need to scroll down when viewing pretty much any web page.
* The spacebar is the largest key. For an application, it makes sense to attach commonly used functionality to this key. For media players this is pause/play. For web browsers this is "scroll down a page", as you'll need to scroll down when viewing pretty much any web page.