So, one of the hassles with jQuery is that you have to include the libraries in script tags on your page in order to use them. This is not a huge deal, but it can be a pain if you want to use the libraries in multiple projects and maintain one central version of the jQuery libraries. That is were the Microsoft AJAX CDN comes into play. It is a Microsoft hosted version of both the AJAX libraries and the jQuery libraries. So, you can point to a Microsoft URL and bring in these libraries. This will find the location that is closest to your user and bring down the libraries from the cache on that server. Should be a much faster solution for everyone. Check out the details on Scott Guthrie’s blog here.