Adjust the feet on you turn tables so the are level. There is a smiple bubble level that looks like a bullseye for less that 3 dollars that is perfect for setting up turntables. If you dont level your turntables you will have problems.

allen

yeah, not having them level will throw your tracking off, and cause your needle to skip more or go screeching across your wax and thats not good. like allen said, most TTs have adjustable feet, if that isnt enough, just slide somethign under the feet to make them level.

I don't imagine 3mm will make that much of a problem, but if you can level them, that would be better.