I've been playing around with Safari in Mavericks, and I've found that when I'm not constantly scrolling and I start reading something for more than about a minute, the app loses focus. This seems to coincide with app nap kicking in. By losing focus I mean just that - by all appearances the window is still in the foreground, but all keyboard input is ignored until the mouse is clicked to "force" the window back into the foreground. This gets very aggravating when I'm trying to read a long dissertation or some complex stuff on the web (or something longer than two paragraphs), as I have to reach over to my mouse just to get my scrolling back. The OS should not be stealing focus on its own like this and preventing keyboard input. Has anybody seen this behaviour and/or found a workaround to this? It truly is frustrating beyond belief.