There seems to be a new icon next to the. Battery icon which looks like a lock with a curved arrow. Don't know what I did to make this appear so I don't know if this is the reason I can't get iPad to go horizontal or not. Help!
Double tap the home button to bring up the recents tray at the bottom. Swipe to the right. The icon all the way on the left side is the screen lock. Tap it to unlock. Then tap the home button again and you are done.
You've got the screen orienation lock on. Turn it off either by the hardware side switch (if you have it set to lock orientation) or on the multi-task area. Double tap the home button, swipe to the right and you'll see it there on the left hand side.