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<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

<title></title>

<script>

var thisPage=false;

window.onbeforeunload=function checkLeave(e){

 var evt = e ? e : (window.event ? window.event : null);        //此方法为了在firefox中的兼容

    if(!thisPage)evt.returnValue='离开会使编写的内容丢失。';

}

</script>

</head>

    <body>

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document.getElementById("mm1").removeChild(document.getElementById("shareDiv"));

<script language="javascript" type="text/javascript" src="http://www.lmjfy.com/Content/jQuery/jquery-1.7.2.min.js"></script>

<input id='up' type="file" />

<a id='btn' href="javascript:void(0);">upload</a>

 <script type="text/javascript">

$(function () {

    $('#btn').click(function(){

$('#up').click();

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});

</script>