screenX clientX pageX概念
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)
参考代码
<!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; width: 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; width: 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>