I look at myself in the mirror everyday, to check my hair set or just to ajust my tie. I think most of the people does at least once a day.
But have you ever wondered why does it reflects us right side left, and not up side down? There was an article that says this mystery has been discussed over and over since the day of ancient Greek. http://mainichi.jp/select/science/news/20071209ddm016040025000c.html (毎日新聞 : 鏡の中：左右逆転の謎 古くはプラトンを悩ませ 今も熱い論争) It says that this mytery has two side of views, physical explanation and psychological explanation.
In physical point of view, I think it is quite a simple question. Why does mirror reflect side ways around and not up side down? Imagine this. If mirror just reflects your figure side ways around, WHY AERN'T YOU SEEING YOUR BACK IN THE MIRROR!? See? Then does it flips front way back? Well, put the mirror on the ground or put it on the ceiling and have a look at it. TADAH! you've made a mirror that shows up side down!
This really simple experiment indicate that saying that mirror reflects side ways around is wrong. It depends on the direction you look into the mirror. Mirror DOES NOT reflects side way around nor even up side down nor front side back.
Then what does mirror do? It reflects as if it turns over the axis the direction of that is perpendicular from the mirror surface. In another word, the mirror reflects plane symmetry. It means that if you put the mirror in front of you, it flips front side back. If you put it on the ceiling, it flips up side down. Got it?