The spider web is probably from a vermetid worm. It spews a web to catch food upon, and reels it in to get its meal.
The other could be a stomatella if it had a small shell on its back that looks like a thumbnail. They move quickly, and if you try to grab it, the tail can fall off like a lizard's. I don't know if the tail grows up to be a new stomatella or not. I never try to remove them if this happens, and hope for the best.