同一页面， 不刷新提交表单

淘宝的产品页面可以实现不刷新就能登陆， 也就是说登陆后整个页面也没有刷新， 请问他是怎么做的呢（大概思路）？我自己觉得他是用了 iframe 的， 然后提交了表单， 
但是用js 好象是没有办法取得 iframe 里面的数据啊，那如果登陆成功后， 又是如何自动关闭当前的浮动层呢（感觉最困惑的地方）？
但是如果不用 iframe 是可以自动关闭当前的浮动层的，因为通过 ajax 可以返回结果， js根据这个结果决定是否关闭当前浮动层，
可是我认为 淘宝用的是 iframe, 困惑中，希望高手解答。。 谢谢~~
下面是淘宝的页面被我给支解了， 留下了这个登陆效果， 请在ie下查看， ff不行<!doctype html>
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img {
border: none;
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display:block;
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<li id="J_PostageCont">
<span>运　　费：</span>读取中...
</li>
</ul>
                                                                          
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<img src="http://assets.taobaocdn.com/sys/common/icon/btn/add_to_recommend.png" alt="加入我的推荐" />
</a>
<a href="http://favorite.taobao.com/popup/add_collection.htm?itemid=9275dca45d7ffe27fa8ef8faa07bf0ba&xid=0db1&itemtype=1&catid=1512&ownerid=1368ceccee1f1064dc05fa791f0f03fd" class="J_PopupTrigger xshop_sc  favorite" data-width="440" data-height="260" data-closebtn="true" title="收藏该宝贝">
<img src="http://assets.taobaocdn.com/sys/common/icon/btn/add_to_fav.png" alt="收藏该宝贝" />
</a><div class="shop-intro-v2">
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<span>收藏本店铺</span>
</a>
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        TB.widget.SimplePopup.decorate(['J_rateTipsL'], 'J_TipsL', {
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YAHOO.util.Event.on('J_rateTipsL', 'click', function(e) {
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            offset: [-75-0, 18],
            autoFit: false,
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            onShow: onShowFunc
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YAHOO.util.Event.on('J_rateTipsR', 'click', function(e) {
            window.open('http://rate.taobao.com/user-rate-1368ceccee1f1064dc05fa791f0f03fd.htm');
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YAHOO.util.Event.onDOMReady(function(){G_sellerInfoFnRight();});
YAHOO.util.Event.onDOMReady(function(){G_sellerInfoFnLeft();});
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        <script type="text/javascript" src="http://assets.taobaocdn.com/app/ishop/stats/isv.js?t=20090403.js"></script>
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    (function () {
        YAHOO.util.Event.onDOMReady(function () {
            TB.ISV.Stat.init({
                nickName:     'kennethlee',        
                userId:       '11671668',        
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