<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <style type="text/css"> *{margin:0px auto; padding:0px;} #shang{width:100%; height:200px; background-color:#CF6;} #caidan{width:100%; height:100px; background-color:#9C0;} .xuanxiang{width:200px; height:100px; background-color:#606; margin-top:20px;} </style> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>无标题文档</title> </head> <body> <div id="shang"></div> <div id="caidan"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> <div class="xuanxiang"></div> </body> <script type="text/javascript"> window.onscroll = function(){ var m = document.getElementById("caidan"); if(window.scrollY>=200){ m.style.position="fixed"; m.style.shang="0px"; }else{ m.style.position=""; } } </script> </html>