A friend and I where just talking about how to keep our dogs away from some areas in our houses and then he was thinking that with cats some people where saying that if you don't won't your cat on the couch spray a mixture of concentrated lime with water around your couch and the cat will avoid it. Is thir any truth in that?

Well I know that my cat wouldn't be bothered by that... if she wants to go on the couch she'll definitely get on the couch one way or another!

Cats are supposed to have an aversion to citrus; but mine doesn't. I sprayed an anti-scratch solution on an area of carpet my cat was clawing at - she sniffed it and rolled on it.

Even if your cat does have the aversion to citrus, it's only going to avoid the area until the smell goes away, so this would not be a long-term solution unless you keep up with the spraying.