If you use the camera's 'Initialize' function, it will return everything back to the way the camera was when it first came out of the box, except that it WON'T delete any images. So that's what I'd do in your situation. (It will probably be far quicker than trying to work out what you've previously pressed in error!):
Press the 'Home' button (at the bottom right, below the big round 'Control' button).
Use the Up and Down buttons (around the edge of the Control Button) to get to 'Main Settings', then press the centre of the Control button.
Then use the same procedure to select 'Initialize'.
The message 'Reset to Default Settings' will appear. Use the Up button to select OK and then the centre button to confirm.
[PS: I disagree with Mjwman. I see no need to format the card, which will delete all of your images, and I can't see how doing so could affect the camera's display settings anyway].