如何实现禁止鼠标拖动复制文档

如何实现禁止鼠标拖动复制文档。（类似www.yesite.com）

你可能发现，有些网站不能够利用鼠标选择要复制的文本内容。是怎么实现的呢，其实是利用一个层。
1。建立一个float.js的文本文件，内容如下：
self.onError=null;
currentX = currentY = 0;
whichIt = null;
lastScrollX = 0; lastScrollY = 0;
NS = (document.layers) ? 1 : 0;
IE = (document.all) ? 1: 0;

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);

2。编写主文件index.html，在<body></body>之间插入以下内容。

<div id=floater style="HEIGHT: 50px; LEFT: -1px; POSITION: absolute; TOP: 19px; WIDTH: 120px; Z-INDEX: 1"></div>
<script language=javascript src="float.js"></script>

=======
就这样，你就发现，在IE浏览器上不能通过拖动鼠标来选择文本了，从而也增加了有心人截获贵网站内容的难度，例子（valley写的一个商业站点：http://www.timemusic.com.cn）