I always assumed that the additional client side DNS lookup would eliminate the increased bandwidth advantage that the CDNs have CDNs offer a bit more than

I always assumed that the additional client side DNS lookup would eliminate the increased bandwidth advantage that the CDNs have CDNs offer a bit more than bandwidth advantage. First, if you have visited a site which used one of these CDNs already it most likely means that your browser won't even send a request for the resource (if CDN sets expire time into the future). Second, even if this will be the first request for a resource it helps to work around the "connections per hostname" limitation in browsers. Let's say your browser allows 4 connections you will be able to fetch four resources in parallel. Using CDN (with a different hostname) allows you to circumvent that. Then your are limited only by total number of connections browser allows and those numbers differ by order of magnitude: 2(IE7) to 6 (IE8, lates FF and Chrome versions) connections per hostname vs. 20 (Opera) to 60 (IE, Safari, Chrome) total connections. Check out http://www.browserscope.org/ http://www.browserscope.org/ — it may give some ideas why Chrome is so fast :)