Cosmetic, I believe. At some point, AFPUB will underscore in red any words that it does not have in its dictionary. If you, for example, go into edit mode and simple erase an errant character, the red line disappears only under the one letter (next to the erased one) - leaving a split red line under a word. What should happen, I think, if the word is now correct, the red line should be entirely removed - showing a correctly spelled word. The red line might disappear when you run through a full document spell check, but I haven't checked that yet.