Monitor Screen Window Adjustment

[Klaatu]

I'm using a Samsung SyncMaster monitor with my MAC Mini (latest OS). I've noticed that the windows on the screen (e.g. Safari or Apple Mail) are wider at the top than the bottom -- is there an adjustment I can make to the screen -- Samsung told me it's a MAC adjustment -- there's no option for making this adjustment with the monitor?

And I've checked in Systems Preferences and couldn't find anything (that doesn't mean it isn't there, but only that I couldn't find it).