I never realized she stayed at the ground floor. When Clark is flying outside her apartment in the pilot I got the impression that it was at least the second floor. Why have four locks on the door if anyone can get in through the window?
Someone asked a FFQ a while back and got quite a few responses. It was a fun discussion.

I found a website with lists of bloopers, the apartment thing being one of them.
Here\'s my post in that thread; it's got a few interesting facts about Lois's apartment quoted from the website I mentioned.
Sara