Thanks for the reply. I took a look at the headers returned for https://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js https://ajax.googleapis.com/aj

Thanks for the reply. I took a look at the headers returned for https://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js https://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.mi... and here's what I see: Content-Type: text/javascript; charset=UTF-8 Last-Modified: Tue, 09 Feb 2010 23:05:02 GMT Date: Mon, 01 Mar 2010 00:09:20 GMT Expires: Mon, 28 Feb 2011 21:55:22 GMT Cache-Control: public, max-age=31536000 Vary: Accept-Encoding X-Content-Type-Options: nosniff Server: sffe Content-Encoding: gzip X-XSS-Protection: 0 200 OK It looks like Google is setting an expires for 1 year in the future, meaning (I believe) that the browser will use the cached copy. So, by using these libraries, you have a decent chance that a brand new visitor will arrive with a warm cache, thereby speeding up that initial page load (and first impression!) a tiny fraction.