Dom中有多种定位属性，下面是一个简单案例
1 <html><!--制作一个会跟着鼠标走的图像，还有控件定位的案例--> 2 <head> 3 <title>document practise</title> 4 <script type="text/javascript"> 5 //document.onclick=function(){alert("点击网页了！");} 6 function increWidth() { 7 var oldwidth = document.getElementById("1").style.width; 8 oldwidth = parseInt(oldwidth) + 50; 9 document.getElementById("1").style.width = oldwidth.toString() + "px"; 10 } 11 document.onmousemove = function () { 12 var x = window.event.clientX; 13 var y = window.event.clientY; 14 var divfly = document.getElementById("fly"); 15 //if (!divfly) return; 16 divfly.style.left = x.toString()+"px"; 17 divfly.style.top= y.toString()+"px"; 18 } 19 20 </script> 21 </head> 22 <body> 23 <input type="button" value="单位" id="1" style="width:50%" /><br /> 24 <input type="button" value="获取单位长度" onclick="alert(document.getElementById(‘1‘).style.width)" /><br /> 25 <input type="button" value="设置单位长度" onclick="document.getElementById(‘1‘).style.width=‘50px‘" /> 26 <input type="button" value="加宽50" onclick="increWidth()" /> 27 <input type="button" value="定位" style="position:fixed;bottom:200px;right:200px;" /> 28 <div id="fly" style="position:absolute"> 29 <img src="../images/front.jpg" width="100" height="120" /> 30 </div> 31 </body> 32 </html>
原文：http://www.cnblogs.com/sytu/p/4090650.html