1 <!DOCTYPE html> 2 <html> 3 <head> 4 <meta charset="utf-8" /> 5 <title>CSS实现div居中</title> 6 <style> 7 /*外层div居中*/ 8 #main { 9 position: absolute; /*极为重要*/ 10 background-color: blue; 11 width:400px; 12 height:200px; 13 left:50%; 14 top:50%; 15 margin-left:-200px; 16 margin-top:-100px; 17 border:1px solid #00F; 18 } 19 20 #content { 21 position: absolute; /*极为重要*/ 22 background-color: yellow; 23 width: 200px; 24 height: 100px; 25 left:50%; 26 top:50%; 27 margin-left:-100px; 28 margin-top:-50px; 29 30 /*div内部文字居中*/ 31 text-align: center; 32 line-height:100px; /*行间距和div高度相同*/ 33 } 34 </style> 35 <body> 36 <div id="main"> 37 <div id="content"> 38 Sun 39 </div> 40 </div> 41 </body> 42 </html>