I believe that skepticism is self refuting. If skeptics assert that you cannot really know something then how do they know you cannot know?
This is a fairly typical misunderstanding of this point. The actual claim is that we have no access to absolute certain knowledge - this esentially comes down to the 'is it a dream?' or 'am I a brain in a vat?' questions. Logically, we cannot be absolutely certain that neither of these things is the case - practically, we assume they are because that is the only reasonable course of action.
We cannot, of course, be certain that absolute certainity is impossible - all we know is that we don't know how to get at it if it is.
Read some Kant.
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