Mac OS X hidden features and nice tips & tricks
"I love the fact that OS X will scroll the window that the mouse is hovering over, even if another application has focus. That way I can scroll an example that I am coding in TextMate without having to lose keyboard control on TM"This also happens on Windows (at least on Chrome) but Windows goes even further: you can click through a link or button on a non-focused window. On OS X, in order to follow a link or click a button on some non-focused window, you need to activate it by clicking and then click again on the desired link/button. This drives me nuts as I found out I use this all the time on Windows. I call this feature "smart focus".