But: Why doesn't /intranet-tmpl/prog/en/lib/yui/ do the job? What's the reason for using an online resource?
You can use the locally hosted YUI files if you prefer. It's entirely up to you. Here's some additional information about why some users choose to go with the Yahoo-hosted files:
"What Are the Benefits of Having Yahoo! Host YUI Files? Yahoo!'s network is located throughout the world. HTTP requests for YUI files are evaluated to determine their geographic source and then served from in-region server farms wherever possible. This edge-computing system provides shorter round-trip times for packets as compared to the use of centralized network hosts. Because YUI files (consisting of JavaScript files, CSS files, and image resources) are static, there need be no relationship between the server providing these files and the server holding session information and business logic for a given application. Moving these files off a central server and closer to your users, therefore, should make your application more responsive overall. Moreover, Yahoo!'s hosting network is configured to serve JavaScript and CSS using gzip compression. We minify YUI JavaScript before pushing it to our servers; in combination with gzipping, this results in a 90% reduction in transmitted filesize as compared to the footprint of YUI's raw (and commented) source. CSS files weigh 60% less on the wire using gzip compression. If your current host does not support mod-gzip or mod-deflate, the advantages of using Yahoo! hosting could be dramatic. (See "YUI: Weighing in on Pageweights" for a full discussion of YUI filesizes.) Finally, far-future Expires headers are issued on all static content. This HTTP response header directs the browser to retain content in cache (and to access it from the cache) as long as possible. Improving your cache hit rate will reduce the amount of time your users spend waiting for files to download." -- Owen -- Web Developer Athens County Public Libraries http://www.myacpl.org