When I worked on disneymoviesonline.go.com we had a very sophisticated build script that would take care of the compression and optimization of CSS and JavaScript. Primarily, we relied on google closure compiler for the the JavaScript optimization and a different method for merging and minifying the CSS. Actually not completely sure what the CSS process entailed, since I came in near the end of the project, I actually had to produce results without knowing the system in and out. No complaints here, really, It’s always a pleasure working on a site that is in production and optimized for millions of page views.
I am quite curious as to how DMO resolved the issue of being stateless and still having an authentication system. Since we are cooking something up right now with Grails, at Disney Advanced Technology, and the back end guys have to integrate spring security and yet keep the app stateless.
Ultimately you are never REALLY stateless. And something like a memcache tier can house the states. What the main issue there is scalability across a load balanced system.
Anyway, what I wanted to mention was that for those of you who are young, and are not relearning a new way to do an old trick, and don’t mind that google will probably replace all this JavaScript stuff wit Dart very soon anyway, you should really take a look at using require.js for CSS optimization during your build process.