The petals are a delicacy for most herbivores (you can put them in salads, too), but I bet it's small snails. The black spots are one of a few fungal spots, some specific to pansies. Control can be effected by the use of sprays, but the best answer is to use good hygiene, avoid buying plants that show any sign, and avoid planting too often in the same ground so the pathogen builds up. Pick off the affected leaves.