CNET has been rooting around in the newly released iOS 4.2 beta and has discovered that the screen orientation lock slider on the right side of the iPad is now a mute button. This would put the iPad in line with all versions of the iPhone. CNET also gives us a misty-eyed look back at the brief history of the screen orientation lock slider's short life. It started out as a volume toggle, then became the screen orientation lock slider that we know and love (or pretty much ignore, in my case!) today, before possibly going on to new heights as a mute button, if the iOS 4.2 beta is anything to go by. However, as CNET points out, it's highly possible that not all the changes made in this first beta will actually be in the final release. CNET also reveals that in the beta, users now have to pull up the new multitasking bar, and swipe left in order to access the screen orientation lock. And it seems that the beta iOS 4.2 also features an iBooks-style brightness slider, which can be used without having to exit the app you're currently using.