网页超过一屏时自动浮动在网页最上方的图层特效 

<!doctype html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>adsorption</title>
 <style type="text/css">
  *{ margin: 0; padding: 0; }
  .header-wrap{ width: 100%; }
  .header-hd{ width: 980px; height: 150px; margin: 0 auto; background-color: #ccc; }
  .header-bd{ width: 980px; height: 40px; margin: 0 auto; background-color: green; }
  .fixed{ position: fixed; width: 100%; }
  .fixed .header-hd{ display: none; }
 </style>

 <script type="text/javascript">
  window.onload=function(){
   function adsorption(){
    var headerWrap=document.getElementById('header-wrap');
    var scrollTop=0;
    window.onscroll=function(){
     scrollTop=document.body.scrollTop||document.documentElement.scrollTop;
     if(scrollTop>100){
      headerWrap.className='fixed';
     }else{
      headerWrap.className='header-wrap';
     }
    }
   }
   adsorption();
  }
 </script>
</head>
<body style="height:3000px;">
 <div id="header-wrap" class="header-wrap">
  <div class="header-hd"></div>
  <div class="header-bd"></div>
 </div>
</body>
</html>

 

posted @ 2014-04-03 12:42  欢醉  阅读(491)  评论(0)  编辑  收藏  举报