Look in this chapter to find answers to questions on:
Q Why didn’t the change I made to my preferences work? I changed a Preferences setting but nothing happened—why?
A While most settings in the Preferences dialog (Command-K [PC: Control-K]) will immediately take effect when you click OK, there are a few that require Photoshop to be restarted for them to take effect. These are: UI Font Size, Scratch Disks, and Memory Usage.
Q What is Column Size in Preferences used for? I see a preference for Column Size, but where I would use that? ...