Power steering problem for SE

I have a question. I have a 2001 Ford Focus SE, and I noticed that my steering wheel squeaks occasionally when I turn the wheel. I looked at my power steering fluid, and it was low, so I took it in to our closest Ford dealership, and they said everything was fine, and they topped off my power steering fluid, but they put in automatic transmission fluid, which I thought was a little bit weird. But since they're the professionals, I just didn't say anything. But now that my "power steering fluid" is full, it still squeaks and I don't know why. They said if it gets low again soon, that I should come in again and have them look at it because it might be a leak. But I don't understand why my steering wheel still squeaks when the power steering fluid is full. Has anyone experienced this problem?

is it the steering wheel or is it up front?
auto tranny fluid works fine in most systems.

you probably have greased ball joints on your steering system. sometimes dust covers will break and the grease will come out, causing major squeaks up front. pinpoint where the sound is coming from and it may be obvoius what is squeaking.