1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>无标题文档</title> 6 <style> 7 #box{ background:red;} 8 #div{width:200px;height:200px;background:blue;margin:100px;} 9 #footer{height:50px;background:yellow;} 10 /* 11 margin传递，子元素的上下margin会传递给父级 12 */ 13 </style> 14 </head> 15 <body> 16 <div id="box"> 17 <div id="div"></div> 18 </div> 19 <div id="footer"></div> 20 </body> 21 </html>
原文：http://www.cnblogs.com/hduhdc/p/5225536.html