Bye bye YUI bloat
I've been doing some serious work this week cutting down on YUI bloat -- our site was including the entire YUI library at the top of every page, at a cost of more than 200k. Worse, because the library was included at the top of every page, the rest of the page had to wait for it to load before it would render.
First, I switched all of our AJAX to use jQuery, the library we've standardized on going forward -- the fact that we had a wrapper function for all of our AJAX calls made this pleasantly easy. Then, I went through the code and figured out which YUI components were being used where. Once that was done, I was able to roll up a few core YUI files into a file to be included in the global header, and call other components only as needed. Total savings: 170k. Holy crap.
By the way, Marcus sent me a link to a great article about why this stuff matters: Use "SCORN" to test the front end of a website for performance by Scott Barber. It's made me get serious about cutting down on our number of HTTP requests, and so far, it seems to be making a difference.