I think I know whats going on. Okay, first off, I bet its when you change something in the table it shifts, not when you change the metatag, i think you may have gotten mixed up.
You're using layers, aren't you, like you say, this layer is located at 120px and 50px? I've had problems when i used dreamweaver in the past, one layer would nudge another. Are you using layers? if so, do you have to? I don't think those are browser friendly (although, i haven't dealt with browser compatability issues since i was a web dev, which was 3 years ago!).