Is it ok if the lid to a slow cooker "rocks" back and forth?

I've never used one of these things before (aka crock pots), but I just bought a little 3 qt one to mess around with. The lip of the ceramic pot must not be even because the gl lid wobbles quite a bit (a few millimeters), so I ume moisture will escape when I'm cooking with it. Is that normal, or does that matter? (on a side note, you can also tell me if you have any favorite things to cook in these, too :).