js 弹出层 并可以拖拽_javascript技巧

<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>弹出层并可拖拽</title> <style> html,body{height:100%;overflow:hidden;} body,div,h2{margin:0;padding:0;} body{font:12px/1.5 Tahoma;} center{padding-top:10px;} button{cursor:pointer;} #overlay{position:absolute;top:0;left:0;width:100%;height:100%;background:#000;opacity:0.5;filter:alpha(opacity=50);display:none;} #win{position:absolute;top:50%;left:50%;width:400px;height:200px;background:#fff;border:4px solid #f90;margin:-102px 0 0 -202px;display:none;} h2{font-size:12px;height:18px;text-align:right;background:#FC0;border-bottom:3px solid #f90;padding:5px;cursor:move;} h2 span{color:#f90;cursor:pointer;background:#fff;border:1px solid #f90;padding:0 2px;} </style> <div id="win"><h2><span id="close">×</span></h2></div> <center><button>弹出层</button></center>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]