var  idTmr  =  "";

function copy(tabid)

{

    var oControlRange = document.body.createControlRange();

    oControlRange.add(tabid,0);

    oControlRange.select();

    document.execCommand("Copy");

}

function toExcel(tabid){

    copy(tabid);

    try

    {

    var xls = new ActiveXObject("Excel.Application");

    }

    catch(e)

    {

    alert( "Excel没有安装或浏览器设置不正确.请启用所有Active控件和插件");

    return false;

}

xls.visible = true;

var xlBook  = xls.Workbooks.Add;

var xlsheet = xlBook.Worksheets(1);

xlBook.Worksheets(1).Activate;

for(var i=0;i<tabid.rows(0).cells.length;i++){

    xlsheet.Columns(i+1).ColumnWidth=15;

}

xlsheet.Paste;

xls=null;

idTmr  =  window.setInterval("Cleanup();",1);  

}

function  Cleanup()  { 

    window.clearInterval(idTmr); 

    CollectGarbage(); 

}

===========================使用示例==============================

<table id="export_table" width="99%" cellspacing="0" cellpadding="0" border="1" style="display:none;">
 <tr>
       <td>1</td>
       <td>2</td>
       <td>3</td>
       <td>4</td>
</tr>
</table>

<input type="button" value="导出Excel" onclick="toExcel(export_table)"/>