如何使页面上的一个层，当滚动垂直滚动条时层也跟着移动（保持相对位置不变）？

<HTML>
<HEAD>
<STYLE TYPE='text/css'>
#myChaser {
position:absolute;
left:200px;
top:0px;
width:250px;
color:#555555;
font-size:12px;
}
</STYLE>
</HEAD><BODY>
<DIV ID='myChaser'>
位置相对固定的层，可以任意设置。</DIV>
<SCRIPT LANGUAGE='JavaScript'>
var oChaser = {
topMargin : 25,
callRate : 10,
slideTime : 1200,
maxDiff : document.all ? document.body.clientHeight : window.innerHeight,
isIE : document.all ? true : false,
chaserDiv : document[document.all ? "all" : "layers"]["myChaser"]
}window.setInterval("oChaser.main( )", oChaser.callRate)
oChaser.main = function( )
{
this.currentY = this.isIE ? this.chaserDiv.style.pixelTop : this.chaserDiv.top
this.scrollTop = this.isIE ? document.body.scrollTop : window.pageYOffset
var newTargetY = this.scrollTop + this.topMargin if ( this.currentY != newTargetY ) { if ( newTargetY != this.targetY ) {
this.targetY = newTargetY
this.slideInit()
}
this.slide()
}
}
oChaser.slideInit = function( )
{
var now = new Date( )
this.A = this.targetY - this.currentY
this.B = Math.PI / ( 2 * this.slideTime )
this.C = now.getTime( ) if (Math.abs(this.A) > this.maxDiff) {
this.D = this.A > 0 ? this.targetY - this.maxDiff : this.targetY + this.maxDiff
this.A = this.A > 0 ? this.maxDiff : -this.maxDiff
} else {
this.D = this.currentY
}
}oChaser.slide = function( )
{
var now = new Date( )
var newY = this.A * Math.sin( this.B * ( now.getTime( ) - this.C ) ) + this.D
newY = Math.round( newY ) if (( this.A > 0 && newY > this.currentY ) ||( this.A < 0 && newY < this.currentY )) {
if ( this.isIE )this.chaserDiv.style.pixelTop = newY
else this.chaserDiv.top = newY
}
}
</SCRIPT>
 
 
 
 
 
</BODY>
</HTML>

解决方案 »

免费领取超大流量手机卡，每月29元包185G流量+100分钟通话, 中国电信官方发货

<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>跟随屏幕移动的图像</title>
<style type="text/css">
#floater {position: absolute;left: 500;top: 146;width: 125;visibility: visible;z-index: 10;}
</style></head><body>
<div ID="floater" style="left: 490px; top: 158px">
<img SRC="clubs.gif" alt="图片显示的文字" WIDTH="225" HEIGHT="160"> 
<table><tr><td height=1000></td></tr></table></div><script LANGUAGE="JavaScript">
function heartBeat() {
if(IE) { diffY = document.body.scrollTop; diffX = document.body.scrollLeft; }
if(NS) { diffY = self.pageYOffset; diffX = self.pageXOffset; }
if(diffY != lastScrollY) {
percent = .1 * (diffY - lastScrollY);
if(percent > 0) percent = Math.ceil(percent);
else percent = Math.floor(percent);
if(IE) document.all.floater.style.pixelTop += percent;
if(NS) document.floater.top += percent;
lastScrollY = lastScrollY + percent;
}
if(diffX != lastScrollX) {
percent = .1 * (diffX - lastScrollX);
if(percent > 0) percent = Math.ceil(percent);
else percent = Math.floor(percent);
if(IE) document.all.floater.style.pixelLeft += percent;
if(NS) document.floater.left += percent;
lastScrollX = lastScrollX + percent;
}
}

function checkFocus(x,y) {
stalkerx = document.floater.pageX;
stalkery = document.floater.pageY;
stalkerwidth = document.floater.clip.width;
stalkerheight = document.floater.clip.height;
if( (x > stalkerx && x < (stalkerx+stalkerwidth)) && (y > stalkery && y < (stalkery+stalkerheight))) return true;
else return false;
}
function grabIt(e) {
if(IE) {
whichIt = event.srcElement;
while (whichIt.id.indexOf("floater") == -1) {
whichIt = whichIt.parentElement;
if (whichIt == null) { return true; }
}
whichIt.style.pixelLeft = whichIt.offsetLeft;
whichIt.style.pixelTop = whichIt.offsetTop;
currentX = (event.clientX + document.body.scrollLeft);
currentY = (event.clientY + document.body.scrollTop);
} else {
window.captureEvents(Event.MOUSEMOVE);
if(checkFocus (e.pageX,e.pageY)) {
whichIt = document.floater;
StalkerTouchedX = e.pageX-document.floater.pageX;
StalkerTouchedY = e.pageY-document.floater.pageY;
}
}
return true;
}
function moveIt(e) {
if (whichIt == null) { return false; }
if(IE) {
newX = (event.clientX + document.body.scrollLeft);
newY = (event.clientY + document.body.scrollTop);
distanceX = (newX - currentX); distanceY = (newY - currentY);
currentX = newX; currentY = newY;
whichIt.style.pixelLeft += distanceX;
whichIt.style.pixelTop += distanceY;
if(whichIt.style.pixelTop < document.body.scrollTop) whichIt.style.pixelTop = document.body.scrollTop;
if(whichIt.style.pixelLeft < document.body.scrollLeft) whichIt.style.pixelLeft = document.body.scrollLeft;
if(whichIt.style.pixelLeft > document.body.offsetWidth - document.body.scrollLeft - whichIt.style.pixelWidth - 20) whichIt.style.pixelLeft = document.body.offsetWidth - whichIt.style.pixelWidth - 20;
if(whichIt.style.pixelTop > document.body.offsetHeight + document.body.scrollTop - whichIt.style.pixelHeight - 5) whichIt.style.pixelTop = document.body.offsetHeight + document.body.scrollTop - whichIt.style.pixelHeight - 5;
event.returnValue = false;
} else {
whichIt.moveTo(e.pageX-StalkerTouchedX,e.pageY-StalkerTouchedY);
if(whichIt.left < 0+self.pageXOffset) whichIt.left = 0+self.pageXOffset;
if(whichIt.top < 0+self.pageYOffset) whichIt.top = 0+self.pageYOffset;
if( (whichIt.left + whichIt.clip.width) >= (window.innerWidth+self.pageXOffset-17)) whichIt.left = ((window.innerWidth+self.pageXOffset)-whichIt.clip.width)-17;
if( (whichIt.top + whichIt.clip.height) >= (window.innerHeight+self.pageYOffset-17)) whichIt.top = ((window.innerHeight+self.pageYOffset)-whichIt.clip.height)-17;
return false;
}
return false;
}
function dropIt() {
whichIt = null;
if(NS) window.releaseEvents (Event.MOUSEMOVE);
return true;
}
if(NS) {
window.captureEvents(Event.MOUSEUP|Event.MOUSEDOWN);
window.onmousedown = grabIt;
window.onmousemove = moveIt;
window.onmouseup = dropIt;
}
if(IE) {
document.onmousedown = grabIt;
document.onmousemove = moveIt;
document.onmouseup = dropIt;
}
if(NS || IE) action = window.setInterval("heartBeat()",1);
// --></script>
</body></html>
<body onscroll="a1.style.top=document.body.scrollTop" onclick=alert(document.body.scrollTop)>
<div id=a1 style="position:absolute;">This is the div</div>
 
 
 
 
 
</body>