<a href="picName.jpg" id=pic1 onclick="savepic();return false;" style="cursor:hand">点击下载</a>

<script type="text/javascript">
function savepic() {
if (document.all.a1 == null) {
objIframe = document.createElement("IFRAME");
document.body.insertBefore(objIframe);
objIframe.outerHTML = "<iframe name=a1 style='width:400px;hieght:300px' src=" + imageName.href + "></iframe>";
re = setTimeout("savepic()", 1)
}
else {
clearTimeout(re)
pic = window.open(imageName.href, "a1")
pic.document.execCommand("SaveAs")
document.all.a1.removeNode(true)
}
}
</script>