Negative margin参考网站

http://coding.smashingmagazine.com/2009/07/27/the-definitive-guide-to-using-negative-margins/

http://www.alistapart.com/articles/negativemargins/

http://www.search-this.com/2007/08/01/the-positive-side-of-negative-margins/(非常好，讲了兄弟之间以及父子之间的关系。。。。。。。)