I don't see any picture, but that doesn't sound good. It's NOT EVER good for water to get into the heater. It means it is not water/air-tight anymore. If it genuinely has condensation inside, I'd unplug it and remove it as soon as possible to avoid current through the water. If you live in a cold area, wrap towels around the tank and put light on it to keep it warm or get a new heater asap.
Another thing... make sure you unplug your heater 10 minutes before you do water changes, as the seals can be weakened/damaged if the heater is running or hot when it becomes unsubmerged.
EDIT: I see a picture in your album now... It looks like condensation, but since I'm not seeing it in person, I can't be sure.