The ranking in the front page is affected by flagging. Usually, the more points a post has and the more recent it is, the higher it is ranked. But flagging pushes it down. So if you see a 100 point post submitted 10 hours ago above a 150 point post submitted 6 hours ago, it means that the 150 point post got flagged a lot.
Posts with much less points are shown higher up in the page than this post. That is usually an indication of the post being flagged.