screenX:鼠标位置相对于用户屏幕水平偏移量，而screenY也就是垂直方向的，此时的参照点也就是原点是屏幕的左上角。
clientX:跟screenX相比就是将参照点改成了浏览器内容区域的左上角，该参照点会随之滚动条的移动而移动。
pageX：参照点也是浏览器内容区域的左上角，但它不会随着滚动条而变动
如图(红点就是鼠标当前位置)
'
缩小浏览器窗口就能看出很明显的差别
示例代码如下：
<!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>
<title></title>
<script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
<style>
body {
margin: 0;
padding: 0;
}
.div {
text-align: center;
font-size: 24px;
height: 300px;
1300px;
line-height: 300px;
color: yellow;
}
#d1 {
background-color: red;
}
#d2 {
background-color: green;
}
#d3 {
background-color: blue;
}
#d4 {
position: absolute;
background-color: yellow;
height: 150px;
120px;
top: 0;
}
</style>
<script type="text/javascript">
$(function () {
window.onscroll = function () {
$("#d4").css("top", getScrollTop());
};
document.onmousemove = function (e) {
if (e == null) {
e = window.event;
}
var html = "screenX:" + e.screenX + "<br/>";
html += "screenY:" + e.screenY + "<br/><br/>";
html += "clientX:" + e.clientX + "<br/>";
html += "clientY:" + e.clientY + "<br/><br/>";
if (e.pageX == null) {
html += "pageX:" + e.x + "<br/>";
html += "pageY:" + e.y + "<br/>";
} else {
html += "pageX:" + e.pageX + "<br/>";
html += "pageY:" + e.pageY + "<br/>";
}
$("#d4").html(html);
};
});
function getScrollTop() {
var top = (document.documentElement && document.documentElement.scrollTop) ||
document.body.scrollTop;
return top;
}
</script>
</head>
<body>
<div id="d1" class="div">div1 height:300px 1300px</div>
<div id="d2" class="div">div2 height:300px 1300px</div>
<div id="d3" class="div">div3 height:300px 1300px</div>
<div id="d4"></div>
</body>
</html>