GMail也是应用了XMLHTTP的嘛？

最近一直在试用GMail，虽然还有很多不稳定和小BUG，但感觉还是很不错的

习惯性的看了下源码，发现：
<title>Gmail</title><noscript>Javascript is disabled in your browser. Gmail requires Javascript to be enabled in order to operate.<p>To use Gmail, enable Javascript by changing your browser preferences.<p>After enabling Javascript, <a href=/gmail>try again</a>.</noscript><script>var testcookie = 'jscookietest=valid';document.cookie = testcookie;if (document.cookie.indexOf(testcookie) == -1) {top.location = '/gmail/html/nocookies.html';}document.cookie = testcookie + ';expires=' + new Date(0).toGMTString();var agt = navigator.userAgent.toLowerCase();if (agt.indexOf('msie')!= -1 && document.all) {var control = (agt.indexOf('msie 5') != -1) ? 'Microsoft.XMLHTTP' : 'Msxml2.XMLHTTP';try {new ActiveXObject(control);} catch (e) {top.location = '/gmail/html/noactivex.html';}}</script><frameset rows='100%,*' border=0><frame name=main src=/gmail/html/loading.html frameborder=0 noresize scrolling=no><frame name=js src=/gmail?view=page&name=js&ver=f68fd517ef5d52be frameborder=0 noresize></frameset>

看这样子，好像是利用到了XMLHTTP的技术来实现了很多页面不刷新的提交工作，请各位专家研究并探讨一下，呵呵