Break Scratch Rules
If you scratch on the break, any ball that drops into a pocket stay pocketed. Your opponent gets the cue ball in hand, places it behind the head string and takes the next shot. The head string is typically indicated at the end of the table, opposite to where the rack is set, by the second small dot or diamond on top of the side rails. When playing eight ball, if you scratch on the break and pocket the eight ball, your opponent has two options -- re-break or shoot after re-spotting the eight ball behind the head string.
Scratch-on-the-Eight-Ball Rule
If you scratch while attempting to pocket the eight ball and the eight ball was not pocketed, you don't lose and the game continues. Your opponent gets the cue ball in hand, places it anywhere on the table and shoots.