Annoying contour

Sometimes when cuting off scanned dark-colored object from a white background I get a one pixel white contour around the object .
Does anyone know how to get rid of it ? thanks in advance .

Select -> modify -> contract.

Enter the ammount of pixels you want to get rid off.
This isn't the best method, I'm sure... it doesn't give you all to clean edges, but it works.

Depending on what you're doing, of course -- but often it's of use to instead of actually cutting off the scanned linework (or what have you) using the blending modes "Multiply" or "Darken."

You can also try inversing the selection, feathering it, and pressing delete. This gives you more of a smooth transition.

Thanks for your help everyone , i'll try all methods .