代码如下: <!DOCTYPE html> <html> <head> <meta charset=”utf-8′′ /> <title>JS实现div居中</title> <style> /*外层div居中*/ #main { position: absolute; /*极为重要*/ background-color: blue; width:400px; height:200px; /*left:50%; top:50%; margin-left:-200px; margin-top:-100px;*/ borde