MacBook Pro Screen Suddenly "Zoomed In"

I've got a two year old MacBook Pro running 10.6.8.

About five minutes ago, while I was using a four-finger trackpad shortcut, the screen suddenly zoomed in about a half inch or so. Now, everything is just slightly lower resolution and my screen is too small to show everything. For example, the date and time in the upper right corner is halfway off the side of the screen. All my desktop icons are slightly larger.

I don't know anything about setting screen resolutions, but I found the display preference and its set for the max 1680x1050. (Seems I remember this once going up to 1080, but maybe I'm mistaken.)

Regardless, my screen is now looking goofy. How do I get it back? And what might I have done to cause this? I don't remember hitting any errant keys of commands, other than using four fingers on the trackpad for a certain function.

-JOHN