Cats and cavaliers
Cavaliers are a breed that tends to get along very well with other animal family members, dogs or cats. However, introductions between a puppy and existing cats, or a new cat/kitten and existing dogs, should always be done carefully, gradually, and with vigilence. The dogs should always be restrained until you know they have become fast friends. Even so, many experienced dog and cat people warn that it is never a good idea to keep a dog and cat together unsupervised in an enclosed area (people with less experience tend to be those who insist there is nothing to be concerned about. Often this ends in an unfortunate way, at best with the wish that they'd listened when people recommened keeping introductions supervised and controlled).
While a dog can do damage to or even kill a cat, a cat can also inflict damage on a cavalier, especially those sensitive eyes. And games can get out of hand; a fleeing cat can seem a bit too much like a hairy chew toy and dogs can get overexcited. If the dog is overexcited and scares the cat, the cat is likely to lash out. Hence it's always good to supervise.
That said (and I am giving a very cautious view deliberately!), I have three cavaliers living happily with several cats and they all get along very well; with a couple of the cats happy to curl up with the cavaliers in the dog or cat beds. :) Most of the time, a harmonious household is really a matter of good sense, a bit of caution, knowing the personalities of your animals, and not rushing things.
Some specific suggestions: I trim the nails on my cats regularly as they are indoor cats (this is easier than it sounds and very easy if you start from kittenhood), and this is a good idea generally if you are mixing cats and dogs. The cat will be well able to protect itself but that very sharp tip will be missing. Believe me, it makes a difference, if you've had a kneading cat in your lap with tips and without! I've had lots of cat and dog wrestling with nary an accident -- the cats seem to be careful and the dogs hold their bite, though again, I supervised initial interactions VERY carefully.
If you have an indoor cat and want to be especially cautious, consider covering your cat's front nails (or all of them) with Soft Paws nail caps: www.softpaws.com (they will ship to Europe too). I have used these; they are very easy to put on with most cats adjusting fairly quickly, last about 2 months per nail, and have the added benefit of keeping your cat from clawing furniture (their main purpose of course!). They even come in colours for those who want stylish cats. :lol: However outdoor cats should never use them as the caps make it very hard for the cat to climb and defend itself if under threat.
Here are a few good links to sites that cover all the information you might want on having a harmonious cat and cavalier household: