OS X Lion is the best version of OS X yet, but some of its design choices aren’t without controversy… especially the decision to make the whole operating system more like iOS.
In OS X Lion, scroll bars don’t exist unless you actually start scrolling. When you start moving up or down in a window, they pop up and function as normal, but it requires that you scroll first before you can actually access the scroll bar.
Here’s how to fix it:
1. Open Applications > System Preferences > General
2. Next to “Show scroll bars” tick the “Always” radio button.
Done! Now, scroll bars will automatically show in Lion as they did in Snow Leopard, even if you haven’t already scrolled.