like people have been saying, they changed a bunch of stuff to avoid being sued by the Stoker family. One of the biggest things they changed, that's still in action today, is the idea that vampires die in sunlight. in Stokers DRACULA, vampires become weaker in daylight, but don't die.

interesting, the family still sued NOSFERATU, won, and all copies were ordered destroyed. a few survived (obviously), and now it's widely seen as a masterpiece.