A phrase often added to the end of a posting where the author isn't certain that what they wrote was correct, or where they expect others to dispute their assertions. It is used as polite way of inviting constructive criticism. Often abbreviated as 'C&CW'.
I've never seen it thus abbreviated. Google search on "c&cw" doesn't get very many hits, but the ones on the first page of hits are unrelated, and kind of amusing in their variety: