Disable expanding scroll bars in Mountain Lion How can I stop the scroll bars in Mountain Lion from expanding when I move my curser over them? 

Sometimes when I try to click on the bottom item in a finder window the scroll bar expands, covering the item, and not allowing the item to be clicked. I have to move the curser away, wait a couple seconds for the scroll bars to hide, then click the item.
In "System Preferences > General" There are three options for "Showing scroll bars". From your description, it sounds like you have the default settings of "Automatically based on mouse or trackpad"



You may find "When Scrolling" or "Always" more to your liking. I'm an old school Mac user, so I have it set to always. That setting solves this problem and other scrolling problems. 

If scroll bars were meant to be hidden, then Andy Hertzfeld would have written them that way in the first place.