This just in:

After years of worry over the effects of man-made chlorofluorocarbons (CFC's) on the ozone layer, a National Oceanic and Atmospheric Administration (NOAA) study has confirmed that the ozone layer decline has stopped declining.  While not necessarily back to its old self, scientists suspect that the ozone layer will begin to thicken again over the next several decades, thanks, they say, to such measures as the 1987 Montreal Protocol, which by international agreement has limited the amount of chlorine and bromine gases released into the atmosphere.

Ozone, or O³, is a molecular bond of three oxygen atoms that forms (and breaks apart) naturally in the atmosphere, and also at Kinkos near the Xerox machines (you'll notice that fresh "copier" smell).  The ozone layer blocks harmful UV radiation from the sun and fluctuates naturally through "complex chemical processes," as the NOAA puts it.  Whether natural processes have influenced the recent decline and stabilization of the ozone layer, and not just CFC's, is debatable.