Why is the accept answer button invisible for new users to this site?

I am using Safari on a Mac Book Air, and for every answer someone posts to my question, the accept answer button is invisible. Maybe this is because I have low rep because I am a new user, but this should be fixed. Otherwise, the only way to accept an answer to blindly click an invisible area below the answerer's vote number.

I don't have this problem on math.SO and puzzling.SO , so I know it is a problem unique with this site that should be fixed. I don't know who to contact to fix this important issue, so I am posting this question here.