offsetTop一开始以为只要容器内div的top定位为负就行，结果今天刚做了个demo，发现好像不是那么回事，于是经过各种测试，得出了一些结论，结论看demo
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" /> <title></title> <style> #aa{width:200px;height:200px;overflow:hidden;float:left;border:2px solid #00f;} #bb{width:200px;height:200px;float:left;margin-left:100px;border:2px solid #00f;} #cc{width:200px;height:200px;float:left;margin-left:100px;border:2px solid #00f;position:relative;} #aaa, #bbb{width:200px;height:500px;background:red;} #ccc{width:200px;height:500px;background:red;position:absolute;top:-200px;} </style> </head> <body> <div id="aa"> <div id="aaa"> 1 <br /> 2 <br /> 3 <br /> 4 <br /> 5 <br /> 6 <br /> 7 <br /> 8 <br /> 9 <br /> 10 <br /> 11 <br /> 12 <br /> 我是aaa </div> </div> <div id="bb"> <div id="bbb"> 1 <br /> 2 <br /> 3 <br /> 4 <br /> 5 <br /> 6 <br /> 7 <br /> 8 <br /> 9 <br /> 10 <br /> 11 <br /> 12 <br /> 我是bbb </div> </div> <div id="cc"> <div id="ccc"> 1 <br /> 2 <br /> 3 <br /> 4 <br /> 5 <br /> 6 <br /> 7 <br /> 8 <br /> 9 <br /> 10 <br /> 11 <br /> 12 <br /> 我是ccc </div> </div> <input type="button" value="看看ccc的scrollTop" onclick="ccc()" /> </body> <script> window.onload = function () { var oDiv = document.getElementById("aa"); var oDiv2 = document.getElementById("bb"); oDiv.scrollTop = 100; oDiv2.scrollTop = 100; } function ccc() { var oDiv = document.getElementById("ccc"); alert(oDiv.scrollTop); } </script> </html>
事实证明，实验才出真理啊，老看书面上的木有用，理解不了它的实际意义