不打开窗口下载文件

<img src="upload/200906081725365867.gif" id="imgIn" />   
<a href="#" onclick="return saveFace(imgIn.src);">保存到电脑</a>   
<iframe name="imgFrame" onload="runSave()" style="display:none;"></iframe>   
   
<script type="text/javascript">   
function runSave(){    
    if (imgFrame.location != "about:blank") window.imgFrame.document.execCommand("SaveAs");    
}    
function saveFace(url){    
    if(window.imgFrame && url) window.imgFrame.location=url;    
    return false;    
}    
</script>