Like most people, I've probably tried 75,000 different things on the carpet to get urine and marking stains out. It's been a trying journey with Rocki who, although he's a bit slow to learn, does understand that he has to go poop outside. However, he never quite grasped the concept that peeing is done outside as well. Although I've tried every which way to train him, it's been a losing battle. So I've come to accept that during the day, Rocki will go outside with his brother and at night, he'll just go wherever and I'll clean it up.
It's not just the stains that drive me nuts - it's the lingering odor that is nauseating and guarantees the dog will return to that exact spot when it comes time to do his or her business. But now I've found something better than my old white vinegar and water solution and it's natural.
I've used this on the bottom of my light colored couch (which is microsuede) and on the carpet. (did I mention the carpet we have left is pale grey? Yellow is quite obvious on it....) This stuff works wonders. I pay about $5.99 for a large spray bottle...I guess it depends on where you buy it. You just spray it on the carpet or furniture and it will remove the odor and the stain.
If the stain is set in, I have had to do more than one treatment. But it does work. The only thing is that when you first spray it on, the urine (or whatever odor is present) gets really strong for a short period of time while the product breaks it down. After that, you don't smell anything. And the nice thing is that this product really doesn't have a smell itself, so you're not covering up the odor with some stupid flowery scent (you know the stuff...you spray it on and later you smell pee AND lilies).
Anyway, this is the website for the company and the product: Nature Clean. Try it...you will like it...and it works.