Home ground advantage is a phenomenon shared by several sport. Recently, my home town baseball team the Philadelphia Phillies completed a 10 game "road" (away) trip where they played 10 games in 3 different cities (and stadiums). They started off well but grew fatigued and did not play well towards the end of the trip. They have come home and played excellently. I can understand these circumstances as the team played a game everyday, and had to travel hundreds of miles between matches and play the very next day. With respect to football and Leeds specifically, we have played much better at home than away. The results show it. It is a little more difficult to understand in football because we play (usually) once a week, and have time to prepare and recover. I want to emphasize that we don't just get better results at home but we actually Play better at home. I don't know why. Some here say its the crowd, Elland Road support is fantastic - but how exactly does that translate to level of play? Is it also because the opposition don't play as well? It is an interesting phenomenon to which which I cannot tender a comprehensive answer.
On the other hand, Wolves played with 5 men at the back against City at Molineux. Lost 0-4. Home ground advantage only goes so far I guess.