Lol you could just google that. It is normally to love long legged girls because it is written in our genes. I don't won't to write here a lot of text here but is connected with evolution of mankind because when young girls start developing in puberty she will probably have longer legs because she isn't fully grown up but again is sexually enough developed. So young teenagers are enough sexually developed so they are healthier and more probable to properly give a birth to a child, so that is why guys find long legs attractive because it is associated to younger and healthier girls. But I always look to a heart not legs :)
If a girl has long legs, I like them well-defined (not Schwarzenegger muscular!) and not too thin. If she has shorter legs, I like it very much if she also has smaller feet; I don't know, I just find this combination very sexy, because it makes the girl look tiny and cute!