Help from the Pedigree website:
"Those of us raised on cartoons have stereotyped ideas about dog-cat relations—and usually they involve images of frightened cats running at light-speed from an angry, onrushing dog. Like most ingrained notions of animal behavior, this one is hard to put behind you. But once you know the truth about canine-feline relationships, you’ll start to see both animals in a new light." There is some intelligent and useful info here: Pedigree
I want to add that our family has had cats and dogs as companions for years. It helps if they're raised together, of course--from kittens and puppies. And sometimes a cat has to teach a puppy manners... As in most cases of introducing interaction, be there! Btw, my German Shepherd, Frosty, got along with our cats beautifully, but she took off after strange cats and chased them as far as she could.