Application windows get smaller and move to corners

gluckmac said:

I'll have three or four application windows on my iMac (latest version of Mountain Lion installed) when suddenly each window gets smaller and moves to a screen corner. The only action I've performed is to move my wireless less than an inch.

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I take it you're new to Lion/Mountain Lion? It seems like you've unknowingly performed the gesture for mission control. You can take a look at the various gestures for your magic mouse/trackpad in System Preferences > Mouse or Trackpad respectively.