DIV层永远居中显示的JS示例
<!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">body,h2{margin:0 ; padding:0;}#faqbg{background-color:#666666; position:absolute; z-index:99; left:0; top:0; display:none; width:100%; height:1200px;opacity:0.5;filter: alpha(opacity=50);-moz-opacity: 0.5;}#faqdiv{position:absolute;width:320px; left:42%; top:10%; margin-left:-100px; height:280px; z-index:100;background-color:#fff; border:1px #8FA4F5 solid; padding:1px;}#faqdiv h2{ height:25px; font-size:12px; background-color:#8FA4F5; position:relative; padding-left:58px; line-height:25px;}#faqdiv h2 a{position:absolute; right:1px; font-size:12px; color:#FF0000}#faqdiv h1 a{position:absolute; left:1px; font-size:12px; color:#FF0000}#faqdiv .form{padding:10px;}</style><script language="JavaScript" type="text/javascript">lastScrollY=0;function heartBeat(){ var diffY;if (document.documentElement && document.documentElement.scrollTop)diffY = document.documentElement.scrollTop;else if (document.body)diffY = document.body.scrollTopelse{}percent=.1*(diffY-lastScrollY); if(percent>0)percent=Math.ceil(percent);else percent=Math.floor(percent); if(percent==null)percent=0;document.getElementById("testdiv").style.top=parseInt(document.getElementById("testdiv").style.top)+percent+"px";lastScrollY=lastScrollY+percent; }window.setInterval("heartBeat()",1);</script></head><body><div id="testdiv" style='left:680px;POSITION:absolute;TOP:150px;z-index: 9999'><br></br><div id="faqdiv" style=""><center><br></br><br></br><input type="text" /><br></br><br></br><input type="button" value="提交" /><br></br></center></div><br></br><br></br></div><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr>111111111111111111111111111111<hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr>222222222222222222222222222222<hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr>333333333333333333333333333333<hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr><hr></body><html>?